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American Civil Liberties Union
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Privacy
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Privacy
The right to privacy is not explicitly identified in the US Constitution, but the ACLU led the charge to establish such rights in the indecisive Poe v. Ullman (1961) case, which addressed a state statute outlawing contraception. The issue arose again in Griswold v. Connecticut (1965), and this time the Supreme Court adopted the ACLU's position and formally declared a right to privacy.Walker, pp. 300–01 The New York affiliate of the ACLU pushed to eliminate anti-abortion laws starting in 1964, a year before Griswold was decided; in 1967 the ACLU itself formally adopted the right to abortion as a policy.Walker, p. 302. The ACLU led the defense in United States v. Vuitch (1971), which expanded the right of physicians to determine when abortions were necessary.Walker, p. 303. These efforts culminated in one of the most controversial Supreme Court decisions, Roe v. Wade (1973), which legalized abortion throughout the United States.Walker, p. 303. The ACLU did not participate directly in Roe v. Wade, but did lead the effort in the companion case Doe v. Bolton. The ACLU successfully argued against state bans on interracial marriage, in the case of Loving v. Virginia (1967).
Related to privacy, the ACLU engaged in several battles to ensure that government records about individuals were kept private and to give individuals the right to review their records. The ACLU supported several measures, including the 1970 Fair Credit Reporting Act, which required credit agencies to divulge credit information to individuals; the 1973 Family Educational Rights and Privacy Act, which provided students the right to access their records; and the 1974 Privacy Act, which prevented the federal government from disclosing personal information without good cause.Walker, p. 308.
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American Civil Liberties Union
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Allegations of bias
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Allegations of bias
In the early 1970s, conservatives and libertarians began to criticize the ACLU for being too political and too liberal.Walker, p. 317. Legal scholar Joseph W. Bishop wrote that the ACLU's trend to partisanship started with its defense of Spock's anti-war protests.Bishop, Joseph W., "Politics and the ACLU", Commentary 52 (December 1971): 50–58. Bishop cited by Walker. Bishop was a professor of law at Yale. Critics also blamed the ACLU for encouraging the Supreme Court to embrace judicial activism.Walker, p. 318. Critics claimed that the ACLU's support of controversial decisions like Roe v. Wade and Griswold v. Connecticut violated the intention of the authors of the Bill of Rights. The ACLU became an issue in the 1988 presidential campaign, when Republican candidate George H. W. Bush accused Democratic candidate Michael Dukakis (a member of the ACLU) of being a "card carrying member of the ACLU".Walker, pp. 319, 363. Bush quoted by Walker.
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American Civil Liberties Union
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Skokie case
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Skokie case
In 1977, the National Socialist Party of America, led by Frank Collin, applied to the town of Skokie, Illinois, for a permit to hold a demonstration in the town park. Skokie at the time had a majority population of Jews, totaling 40,000 of 70,000 citizens, some of whom were survivors of Nazi concentration camps. Skokie refused to grant the NSPA a permit and passed ordinances against hate speech and military wear, in addition to requiring an insurance bond. Skokie's Village Council ordered village attorney, Harvey Schwartz, to seek an injunction to stop the demonstration. The ACLU assisted Collin and appealed to federal court, eventually prevailing in NSPA v. Village of Skokie.Ed McManus, "Nazi March: What's It All About?", Illinois Issues, v.13, Nov. 1978 (available at Illinois Periodicals Online ).The federal appeal case was Smith v. Collin 447 F. Supp. 676. See also Supreme Court: Smith v. Collin, 439 US 916 (1978), and National Socialist Party v. Skokie, 432 US 43 (1977).
The Skokie case was heavily publicized across America, partially because Jewish groups such as the Jewish Defense League and Anti Defamation League strenuously objected to the demonstration, leading many members of the ACLU to cancel their memberships. The Illinois affiliate of the ACLU lost about 25% of its membership and nearly one-third of its budget.30,000 ACLU members resigned in protest.Philippa Strum, When the Nazis Came to Skokie: Freedom for Speech We Hate (University Press of Kansas) (University of Kansas Press publisher's catalog description ). The financial strain from the controversy led to layoffs at local chapters. After the membership crisis died down, the ACLU sent out a fund-raising appeal which explained their rationale for the Skokie case and raised over $500,000 ($ in dollars).Walker, p. 239.
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American Civil Liberties Union
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1980s
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1980s
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American Civil Liberties Union
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Reagan era
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Reagan era
thumb|upright|The ACLU defended Oliver North in 1990, arguing that his conviction was tainted by coerced testimony.
The inauguration of Ronald Reagan as president in 1981 ushered in an eight-year period of conservative leadership in the US government. Under Reagan's leadership, the government pushed a conservative social agenda.
The Arkansas 1981 creationism statute, which required schools to teach the biblical account of creation as a scientific alternative to evolution. The ACLU won the case in the McLean v. Arkansas decision.Walker, pp. 342–43.McLean v. Arkansas Board of Education, 529 F. Supp. 1255 (E.D. Ark. 1982) ("transcription" by Clark Dorman, January 30, 1996, at TalkOrigins).
In 1982, the ACLU became involved in a case involving the distribution of child pornography (New York v. Ferber). In an amicus brief, the ACLU argued that child pornography that violates the three prong obscenity test should be outlawed. However, the law was overly restrictive because it banned artistic displays and non-obscene material. The court did not adopt the ACLU's position.
During the 1988 presidential election, Vice President George H. W. Bush noted that his opponent Massachusetts Governor Michael Dukakis had described himself as a "card-carrying member of the ACLU" and used that as evidence that Dukakis was "a strong, passionate liberal" and "out of the mainstream". The phrase subsequently was used by the organization in an advertising campaign.
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American Civil Liberties Union
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1990s
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1990s
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American Civil Liberties Union
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Free speech
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Free speech
In 1997, ruling unanimously in the case of Reno v. American Civil Liberties Union, the Supreme Court voided the anti-indecency provisions of the Communications Decency Act (the CDA), finding they violated the freedom of speech provisions of the First Amendment. In their decision, the Supreme Court held that the CDA's "use of the undefined terms 'indecent' and 'patently offensive' will provoke uncertainty among speakers about how the two standards relate to each other and just what they mean."
In 2000, Marvin Johnson, a legislative counsel for the ACLU, stated that proposed anti-spam legislation infringed on free speech by denying anonymity and by forcing spam to be labeled as such, "Standardized labeling is compelled speech." He also stated, "It's relatively simple to click and delete."Adam S. Marlin, "First Amendment is obstacle to spam legislation" , CNN, June 9, 2000. The debate found the ACLU joining with the Direct Marketing Association and the Center for Democracy and Technology in 2000 in criticizing a bipartisan bill in the House of Representatives. As early as 1997, the ACLU had taken a strong position that nearly all spam legislation was improper, although it has supported "opt-out" requirements in some cases. The ACLU opposed the 2003 CAN-SPAM actACLU, "Letter to the Senate Urging Opposition to S.877, the "Controlling the Assault of Non-Solicited Pornography and Marketing Act of 2003"" , July 30, 2003 (last visited January 7, 2008). suggesting that it could have a chilling effect on speech in cyberspace. It has been criticized for this position.
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American Civil Liberties Union
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2000s
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2000s
In 2006, the ACLU of Washington State joined with a pro-gun rights organization, the Second Amendment Foundation, and prevailed in a lawsuit against the North Central Regional Library District (NCRL) in Washington for its policy of refusing to disable restrictions upon an adult patron's request. Library patrons attempting to access pro-gun web sites were blocked, and the library refused to remove the blocks.Bradburn et al. v. North Central Regional Library District (US District Court, Eastern District of Washington), In 2012, the ACLU sued the same library system for refusing to disable temporarily, at the request of an adult patron, Internet filters which blocked access to Google Images."Internet Porn is Subject of ACLU lawsuit", International Business Times, February 3, 2012.
In 2006, the ACLU challenged a Missouri law prohibiting picketing outside veterans' funerals. The ACLU filed the suit in support of the Westboro Baptist Church and Shirley Phelps-Roper, who were threatened with arrest.Garance Burke, "ACLU Sues for Anti-Gay Group That Pickets at Troops' Burials", The Washington Post, July 23, 2006.The ACLU challenged the Missouri law, which was similar to the federal Respect for America's Fallen Heroes Act. The Westboro Baptist Church is well known for its picket signs that contain messages such as "God Hates Fags", "Thank God for Dead Soldiers", and "Thank God for 9/11". The ACLU issued a statement calling the legislation a "law that infringes on Shirley Phelps-Roper's rights to religious liberty and free speech.""ACLU of Eastern Missouri Challenges Law Banning Pickets and Protests One Hour Before or After a Funeral" , ACLU, July 21, 2006. The ACLU prevailed in the lawsuit.
The ACLU argued in an amicus brief to the Supreme Court that a decision on the constitutionality of a Massachusetts law required the consideration of additional evidence because lower courts have undervalued the right to engage in sidewalk counseling. The law prohibited sidewalk counselors from approaching women outside abortion facilities and offering them alternatives to abortion but allowed escorts to speak with them and accompany them into the building. In overturning the law in McCullen v. Coakley, the Supreme Court unanimously ruled that it violated the counselors' freedom of speech and constituted viewpoint discrimination.
In 2009, the ACLU filed an amicus brief in Citizens United v. FEC, arguing that the Bipartisan Campaign Reform Act of 2002 violated the First Amendment right to free speech by curtailing political speech. This stance on the landmark Citizens United case caused considerable disagreement within the organization, resulting in a discussion about its future stance during a quarterly board meeting in 2010. On March 27, 2012, the ACLU reaffirmed its stance in support of the Supreme Court's Citizens United ruling, at the same time voicing support for expanded public financing of election campaigns and stating the organization would firmly oppose any future constitutional amendment limiting free speech.
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American Civil Liberties Union
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2010s
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2010s
In 2012, the ACLU filed suit on behalf of the Ku Klux Klan of Georgia, claiming that the KKK was unfairly rejected from the state's "Adopt-a-Highway" program. The ACLU prevailed in the lawsuit.
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American Civil Liberties Union
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Allegations of prioritizing civil rights over civil liberties{{Anchor
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Allegations of prioritizing civil rights over civil liberties
Some have claimed the ACLU is reducing its support of unpopular free speech (specifically, by declining to defend speech made by conservatives) in favor of identity politics, political correctness, and progressivism.
Instead, critics contend that the organization has become a progressive advocacy organization intensely focused on identity politics.
One basis of these allegations was a 2017 statement the ACLU president made to a reporter after the death of a counter-protester during the 2017 Unite the Right rally in Virginia, where Romero told a reporter that the ACLU would no longer support legal cases of activists that wish to carry guns at their protests. Another basis for these claims was an internal ACLU memo dated June 2018, discussing factors to evaluate when deciding whether to take a case. The memo listed several factors to consider, including "the extent to which the speech may assist in advancing the goals of white supremacists or others whose views are contrary to our values."
Some analysts viewed this as a retreat from the ACLU's historically strong support of First Amendment rights, regardless of whether minorities were negatively impacted by the speech, citing the ACLU's past support for certain KKK and Nazi legal cases. The memo's authors stated that the memo did not define a change in official ACLU policy, but was intended as a guideline to assist ACLU affiliates in deciding which cases to take.
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American Civil Liberties Union
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2020s
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2020s
In 2021, the ACLU responded to the criticisms by denying that they are reducing their support for unpopular First Amendment causes and listing 27 cases from 2017 to 2021 where the ACLU supported a party holding an unpopular or repugnant viewpoint. The cases included one which challenged college restrictions on hate speech; a case defending a Catholic school's right to discriminate in hiring; and a case that defended antisemitic protesters who marched outside a synagogue.
In 2024, the National Labor Relations Board sued the ACLU in an unfair labor practice case after the ACLU fired an Asian attorney for criticizing her Black bosses. The ACLU contended that the employee's use of phrases like "the beatings will continue until morale improves" was racially coded and that it "caused serious harm to Black members of the ACLU community." According to Jeremy W. Peters of The New York Times, critics of the ACLU saw the firing as "a sign of how far the group has strayed from its core mission — defending free speech — and has instead aligned itself with a progressive politics that is intensely focused on identity."
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American Civil Liberties Union
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LGBTQ issues
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LGBTQ issues
In 2000, the ACLU lost the Boy Scouts of America v. Dale case, which had asked the Supreme Court to require the Boy Scouts of America to drop their policy of prohibiting homosexuals from becoming Boy Scout leaders.ACLU, "U.S. Supreme Court Ruling that Boy Scouts Can Discriminate Is 'Damaging but Limited,' ACLU Says" , June 28, 2000 (last visited October 26, 2009).
In March 2004, the ACLU, along with Lambda Legal and the National Center for Lesbian Rights, sued the state of California on behalf of six same-sex couples who were denied marriage licenses. That case, Woo v. Lockyer, was eventually consolidated into In re Marriage Cases, the California Supreme Court case which led to same-sex marriage being available in that state from June 16, 2008, until Proposition 8 was passed on November 4, 2008."California Marriage Case", ACLU, retrieved June 28, 2009 The ACLU, Lambda Legal and the National Center for Lesbian Rights then challenged Proposition 8"California's Prop 8 Update", ACLU, November 6, 2008. and won."Federal Appeals Court Says California Marriage Ban Is Unconstitutional" , ACLU, February 7, 2012.
In 2011, the ACLU started its Don't Filter Me project, countering LGBT-related Internet censorship in public schools in the United States.
On January 7, 2013, the ACLU settled with the federal government in Collins v. United States that provided for the payment of full separation pay to servicemembers discharged under "don't ask, don't tell" since November 10, 2004, who had previously been granted only half that.
In 2021, the ACLU filed a brief siding with a school district that had a policy of using preferred pronouns for transgender students. Some analysts felt this was a retreat from the ACLU's historical defense of the First Amendment because the ACLU was opposing the teachers who were disciplined for refusing to use the preferred pronouns.
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American Civil Liberties Union
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Anti-terrorism issues
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Anti-terrorism issues
thumb|upright|The ACLU represented Internet service provider Nicholas Merrill in a 2004 lawsuit which challenged the government's right to gather information about Internet access secretly.
After the September 11 attacks, the federal government instituted a broad range of new measures to combat terrorism, including the passage of the Patriot Act. The ACLU challenged many of the measures, claiming that they violated rights regarding due process, privacy, illegal searches, and cruel and unusual punishment. An ACLU policy statement states:
During the ensuing debate regarding the proper balance of civil liberties and security, the membership of the ACLU increased by 20%, bringing the group's total enrollment to 330,000. The growth continued, and by August 2008 ACLU membership was greater than 500,000. It remained at that level through 2011.ACLU, "About Us"
The ACLU has been a vocal opponent of the Patriot Act of 2001, the PATRIOT 2 Act of 2003, and associated legislation made in response to the threat of domestic terrorism. In response to a requirement of the USA PATRIOT Act, the ACLU withdrew from the Combined Federal Campaign charity drive.ACLU, "Citing Government "Blacklist"; Policy, ACLU Rejects $500,000 from Funding Program " , July 31, 2004 (last visited January 7, 2008). The campaign required ACLU employees to be checked against a federal anti-terrorism watch list. The ACLU has stated that it would "reject $500,000 in contributions from private individuals rather than submit to a government 'blacklist' policy".
In 2004, the ACLU sued the federal government in American Civil Liberties Union v. Ashcroft on behalf of Nicholas Merrill, owner of an Internet service provider. Under the provisions of the Patriot Act, the government had issued national security letters to Merrill to compel him to provide private Internet access information from some of his customers. In addition, the government placed a gag order on Merrill, forbidding him from discussing the matter with anyone.
In January 2006, the ACLU filed a lawsuit, ACLU v. NSA, in a federal district court in Michigan, challenging government spying in the NSA warrantless surveillance (2001–2007) controversy.Complaint for Declaratory and Injunctive Relief ("NSA Spying Complaint"), ACLU v. NSA (E.D. Mich. January 17, 2006) (PDF of complaint available at ACLU website, "Safe and Free: NSA Spying" section of website). On August 17, 2006, that court ruled that the warrantless wiretapping program was unconstitutional and ordered it ended immediately.Ryan Singel, "Judge Halts NSA Snooping", Wired, August 17, 2006. However, the order was stayed pending an appeal. The Bush administration did suspend the program while the appeal was being heard. In February 2008, the US Supreme Court turned down an appeal from the ACLU to let it pursue a lawsuit against the program that began shortly after the September 11 terror attacks.
The ACLU and other organizations also filed separate lawsuits against telecommunications companies. The ACLU filed a lawsuit in Illinois (Terkel v. AT&T), which was dismissed because of the state secrets privilege"ACLU of Illinois Responds to Ruling in Terkel v. AT&T , ACLU, July 25, 2006, retrieved January 7, 2008 and two others in California requesting injunctions against AT&T and Verizon."ACLU Files Lawsuit in California Court Demanding End to Privacy Violations by AT&T and Verizon" , ACLU, May 26, 2006, retrieved January 7, 2008 On August 10, 2006, the lawsuits against the telecommunications companies were transferred to a federal judge in San Francisco.
The ACLU represents a Muslim-American who was detained but never accused of a crime in Ashcroft v. al-Kidd, a civil suit against former Attorney General John Ashcroft. In January 2010, the American military released the names of 645 detainees held at the Bagram Theater Internment Facility in Afghanistan, modifying its long-held position against publicizing such information. This list was prompted by a Freedom of Information Act lawsuit filed in September 2009 by the ACLU, whose lawyers had also requested detailed information about conditions, rules, and regulations.
On August 10, 2020, in an opinion article for USA Today by Anthony D. Romero, the ACLU called for the dismantling of the United States Department of Homeland Security over the deployment of federal forces in July 2020 during the George Floyd protests. On August 26, 2020, the ACLU filed a lawsuit on behalf of seven protesters and three veterans following the protests in Portland, Oregon, which accused the Trump Administration of using excessive force and unlawful arrests with federal officers.
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American Civil Liberties Union
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Trump administration
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Trump administration
thumb|left|Abdi Soltani, executive director of Northern California ACLU, speaks at a San Francisco protest of the U.S. immigration ban.
Following Donald Trump's election as president on November 8, 2016, the ACLU responded on Twitter by saying: "Should President-elect Donald Trump attempt to implement his unconstitutional campaign promises, we'll see him in court." On January 27, 2017, President Trump signed an executive order indefinitely barring "Syrian refugees from entering the United States, suspended all refugee admissions for 120 days and blocked citizens of seven Muslim-majority countries, refugees or otherwise, from entering the United States for 90 days: Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen". The ACLU responded by filing a lawsuit against the ban on behalf of Hameed Khalid Darweesh and Haider Sameer Abdulkhaleq Alshawi, who had been detained at JFK International Airport. On January 28, 2017, District Court Judge Ann Donnelly granted a temporary injunction against the immigration order, saying it was difficult to see any harm from allowing the newly arrived immigrants to remain in the country. In response to Trump's order, the ACLU raised more than $24 million from more than 350,000 individual online donations in two days. This amounted to six times what the ACLU normally receives in online donations in a year. Celebrities donating included Chris Sacca (who offered to match other people's donations and ultimately gave $150,000), Rosie O'Donnell, Judd Apatow, Sia, John Legend, and Adele. The number of members of the ACLU doubled in the time from the election to end of January to 1 million.
Grants and contributions increased from US$106 million reported by the 2016 year-end income statement to $274 million by the 2017 year-end statement. The segment's primary revenue source came from individual contributions in response to the Trump presidency's infringements on civil liberties. Besides filing more lawsuits than during previous presidential administrations, the ACLU has spent more money on advertisements and messaging as well, weighing in on elections and pressing political concerns. This increased public profile has drawn some accusations that the organization has become more politically partisan than in previous decades.
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American Civil Liberties Union
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Israel–Palestine
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Israel–Palestine
In 2022, the ACLU petitioned the US Supreme Court to overturn an Arkansas anti-BDS law mandating that companies pledge not to boycott Israel in order to do business with the state.
During the Gaza war, the New York chapter of the ACLU sued Columbia University for banning its campus chapters of Jewish Voice for Peace and Students for Justice in Palestine on the grounds of First Amendment violations. In February 2024, the ACLU signed a letter to US Secretary of Education Miguel Cardona calling on him to reject redefining antisemitism to include political criticism of the government of the state of Israel, saying it would lead to First Amendment violations. The ACLU also rejected a staff petition urging the organization to oppose U.S. military aid to Israel and divest from potential financial ties to the country. In a 50–4 vote, with one abstention, the board stated that their mission focuses on U.S. civil rights, as an ACLU spokesperson stated "it is not the ACLU's practice to take positions on overseas conflicts." Nearly 700 staff members stated that the ACLU had previously taken stances on global issues like the Vietnam War and South African apartheid.
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American Civil Liberties Union
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Social media
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Social media
In 2024, the ACLU spoke out against governments banning the social media platform TikTok. The organization specifically condemned a U.S. House bill banning the platform in March 2024, calling the legislation "unconstitutional." In December 2024, the ACLU criticized a federal appeals court ruling that upheld the law, claiming it "sets a flawed and dangerous precedent, one that gives the government far too much power to silence Americans' speech online."
The ACLU has also lobbied against the Kids Online Safety Act, a bill meant to protect children online. The organization claims it would censor important conversations online, particularly among marginalized groups.
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American Civil Liberties Union
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See also
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See also
American Civil Rights Union
British Columbia Civil Liberties Association
Canadian Civil Liberties Association
Common Cause
Foundation for Individual Rights and Expression (FIRE)
Institute for Justice
Liberty, a British equivalent
List of court cases involving the American Civil Liberties Union
National Emergency Civil Liberties Committee
Political freedom
Southern Poverty Law Center
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American Civil Liberties Union
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Citations
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Citations
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American Civil Liberties Union
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General and cited references
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General and cited references
Bodenhamer, David, and Ely, James, Editors (2008). The Bill of Rights in Modern America, second edition. Indiana University Press. .
Donohue, William (1985). The Politics of the American Civil Liberties Union. Transaction Books. .
Kaminer, Wendy (2009). Worst Instincts: Cowardice, Conformity, and the ACLU. Beacon Press. . A dissident member of the ACLU criticizes its post-9/11 actions as betraying the core principles of its founders.
Lamson, Peggy (1976). Roger Baldwin: Founder of the American Civil Liberties Union. Houghton Mifflin Company. .
Walker, Samuel (1990). In Defense of American Liberties: A History of the ACLU. Oxford University Press. .
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American Civil Liberties Union
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Further reading
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Further reading
Klein Woody, and Baldwin, Roger Nash (2006). Liberties lost: the endangered legacy of the ACLU. Greenwood Publishing Group, 2006. A collection of essays by Baldwin, each accompanied by commentary from a modern analyst.
Krannawitter, Thomas L. and Palm, Daniel C. (2005). A Nation Under God?: The ACLU and religion in American politics. Rowman & Littlefield.
Sears, Alan, and Osten, Craig (2005). The ACLU vs America: Exposing the Agenda to Redefine Moral Values. B&H Publishing Group.
Smith, Frank LaGard (1996). ACLU: The Devil's Advocate: The Seduction of Civil Liberties in America. Marcon Publishers.
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American Civil Liberties Union
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Archives
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Archives
American Civil Liberties Union of Southern California records. 754 boxes. UCLA Library Special Collections.
American Civil Liberties Union of Washington. 1917–2019. 188.31 cubic feet (including 13 microfilm reels and 1 videocassette) plus 62 cartons and 2 rolled posters. Labor Archives of Washington. University of Washington Special Collections.
American Civil Liberties Union of Michigan: Detroit Branch Records 1952–1966. This collection documents the early years of the Detroit ACLU branch. The collection contains documents related to academic freedom; censorship; church and state; civil liberties; police brutality; HUAC; and legal assistance to prisoners. Walter P. Reuther Library, Detroit, Michigan.
American Civil Liberties Union of Oakland County, Michigan 1970–1984. This collection illustrates that the branch was formed to address Oakland County jail conditions, lie detector use, senior housing rights, and attempts to reinstate the death penalty. Walter P. Reuther Library, Detroit, Michigan.
American Civil Liberties Union Records, Princeton University. Document archive 1917–1950, including the history of the ACLU.
Debs Pamphlet Collection , Indiana State University Library. An array of annual ACLU reports in PDF.
List of 100 most important ACLU victories (through 2002) by New Hampshire Civil Liberties Union
De-classified records on the ACLU, FBI
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American Civil Liberties Union
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Selected works sponsored or published by the ACLU
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Selected works sponsored or published by the ACLU
Annual Report – American Civil Liberties Union, American Civil Liberties Union, 1921.
Black Justice, ACLU, 1931.
How Americans Protest, American Civil Liberties Union, 1963.
Secret detention by the Chicago police: a report, American Civil Liberties Union, 1959.
Report on lawlessness in law enforcement, Wickersham Commission, Patterson Smith, 1931. This report was written by the ACLU but published under the auspices of the Wickersham Commission.
Miller, Merle, (1952), The Judges and the Judged, Doubleday.
ACLU organization records, 1947–1995. Princeton University Library, Mudd Manuscript Library.
The Dangers of Domestic Spying by Federal Law Enforcement, American Civil Liberties Union, 2002.
Engines of Liberty: The Power of Citizen Activists to Make Constitutional Law, David D. Cole, 2016
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American Civil Liberties Union
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External links
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External links
Category:Civil rights organizations in the United States
Category:1920 establishments in the United States
Category:501(c)(4) nonprofit organizations
Category:Abortion-rights organizations in the United States
Category:Civil liberties advocacy groups in the United States
Category:Drug policy reform
Category:Government watchdog groups in the United States
Category:Identity politics in the United States
Category:Immigration political advocacy groups in the United States
Category:Legal advocacy organizations in the United States
Category:LGBTQ political advocacy groups in the United States
Category:Non-profit organizations based in New York City
Category:Law firms based in New York City
Category:Organizations established in 1920
Category:Privacy in the United States
Category:Privacy organizations
Category:Transgender organizations in the United States
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American Civil Liberties Union
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Table of Content
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Short description, Leadership, Funding, Policy positions, Support and opposition, Organization and state affiliants, List of ACLU state affiliates, History, 1910s and '20s, Origins, Free speech era, Public schools, Free speech expansion, 1930s, Communism and totalitarianism, 1940s, World War II, Cold War era, 1950s, McCarthy era, 1960s, Racial discrimination, Police misconduct, Civil liberties revolution, Vietnam War, 1970s, Watergate era, Enclaves and new civil liberties, Victim groups, Reproductive Freedom Project, Privacy, Allegations of bias, Skokie case, 1980s, Reagan era, 1990s, Free speech, 2000s, 2010s, Allegations of prioritizing civil rights over civil liberties{{Anchor, 2020s, LGBTQ issues, Anti-terrorism issues, Trump administration, Israel–Palestine, Social media, See also, Citations, General and cited references, Further reading, Archives, Selected works sponsored or published by the ACLU, External links
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Adobe Inc.
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Short description
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Adobe Inc. ( ), formerly Adobe Systems Incorporated, is an American computer software company based in San Jose, California. It offers a wide range of programs from web design tools, photo manipulation and vector creation, through to video/audio editing, mobile app development, print layout and animation software.
It has historically specialized in software for the creation and publication of a wide range of content, including graphics, photography, illustration, animation, multimedia/video, motion pictures, and print. Its flagship products include Adobe Photoshop image editing software; Adobe Illustrator vector-based illustration software; Adobe Acrobat Reader and the Portable Document Format (PDF); and a host of tools primarily for audio-visual content creation, editing and publishing. Adobe offered a bundled solution of its products named Adobe Creative Suite, which evolved into a subscription-based offering named Adobe Creative Cloud. The company also expanded into digital marketing software and in 2021 was considered one of the top global leaders in Customer Experience Management (CXM).
Adobe was founded in December 1982 by John Warnock and Charles Geschke, who established the company after leaving Xerox PARC to develop and sell the PostScript page description language. In 1985, Apple Computer licensed PostScript for use in its LaserWriter printers, which helped spark the desktop publishing revolution. Adobe later developed animation and multimedia through its acquisition of Macromedia, from which it acquired Macromedia Flash; video editing and compositing software with Adobe Premiere, later known as Adobe Premiere Pro; low-code web development with Adobe Muse; and a suite of software for digital marketing management.
Adobe had more than 26,000 employees worldwide. Adobe also has major development operations in the United States in Newton, New York City, Arden Hills, Lehi, Seattle, Austin and San Francisco. It also has major development operations in Noida and Bangalore in India. The company has long been the dominant tech firm in design and creative software, despite attracting criticism for its policies and practices particularly around Adobe Creative Cloud's switch to subscription only pricing and its early termination fees for its most promoted Creative Cloud plan, the latter of which attracted a joint civil lawsuit from the US Federal Trade Commission and the U.S. Department of Justice in 2024.
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Adobe Inc.
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History
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History
right|thumb|Logo of Adobe Systems, 1982–1993
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Adobe Inc.
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PostScript (1982–1986)
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PostScript (1982–1986)
The company was started in John Warnock's garage. The name of the company, Adobe, comes from Adobe Creek in Los Altos, California, a stream which ran behind Warnock's house. The creek is named because of the type of clay found there (Adobe being a Spanish word for Mudbrick). Adobe's corporate logo features a stylized "A" and was designed by graphic designer Marva Warnock, John Warnock's wife. Steve Jobs attempted to buy the company for $5 million in 1982, but Warnock and Geschke refused. Their investors urged them to work something out with Jobs, so they agreed to sell him shares worth 19 percent of the company. Jobs paid a five-times multiple of their company's valuation at the time, plus a five-year license fee for PostScript, in advance. The purchase and advance made Adobe the first company in the history of Silicon Valley to become profitable in its first year.
Warnock and Geschke considered various business options including a copy-service business and a turnkey system for office printing. Then they chose to focus on developing specialized printing software and created the Adobe PostScript page description language.
PostScript was the first international standard for computer printing as it included algorithms describing the letter-forms of many languages. Adobe added kanji printer products in 1988. Warnock and Geschke were also able to bolster the credibility of PostScript by connecting with a typesetting manufacturer. They weren't able to work with Compugraphic, but then worked with Linotype to license the Helvetica and Times Roman fonts (through the Linotron 100). By 1987, PostScript had become the industry-standard printer language with more than 400 third-party software programs and licensing agreements with 19 printer companies.
Adobe's first products after PostScript were digital fonts which they released in a proprietary format called Type 1, worked on by Bill Paxton after he left Stanford. Apple subsequently developed a competing standard, TrueType, which provided full scalability and precise control of the pixel pattern created by the font's outlines, and licensed it to Microsoft.
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Adobe Inc.
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Introduction of creative software (1986–1996)
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Introduction of creative software (1986–1996)
Starting in the mid-1980s, Adobe entered the consumer software market, starting with Adobe Illustrator, a vector-based drawing program for the Apple Macintosh. Illustrator, which grew out of the firm's in-house font-development software, helped popularize PostScript-enabled laser printers.
By the mid-1990s, Adobe would either develop or acquire Photoshop from John and Thomas Knoll, FrameMaker from Frame Technology Corporation, and After Effects and PageMaker from Aldus, as well as develop Adobe Premiere, later known as Premiere Pro, in-house, initially releasing it in 1991. Around the same time as the development of Illustrator, Adobe entered the NASDAQ Composite index in August 1986.
left|thumb|Logo of Adobe Inc., 1993–2017|186x186px
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Adobe Inc.
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PDFs and file formats (1993–1999)
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PDFs and file formats (1993–1999)
In 1993, Adobe introduced the Portable Document Format, commonly shortened to the initialism PDF, and its Adobe Acrobat and Reader software. Warnock originally developed the PDF under a code name, "The Camelot Project", using PostScript technology to create a widely available digital document format, able to display text, raster graphics, vector graphics, and fonts. Adobe kept the PDF as a proprietary file format from its introduction until 2008, when the PDF became an ISO international standard under ISO number ISO 32000-1:2008, though the PDF file format was free for viewers since its introduction.
With its acquisition of Aldus, in addition to gaining PageMaker and After Effects, Adobe gained control over the TIFF file format for images.
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Adobe Inc.
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Creative Suite and the Macromedia acquisition (2000–2009)
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Creative Suite and the Macromedia acquisition (2000–2009)
The 2000s saw various developments for the company. Its first notable acquisition in the decade was in 2002, when Adobe acquired Canadian company Accelio, also known as JetForm. In May 2003, Adobe purchased audio editing and multitrack recording software Cool Edit Pro from Syntrillium Software for $16.5 million, as well as a large loop library called "Loopology". Adobe then renamed Cool Edit Pro to Adobe Audition. It was in 2003 that the company introduced the first version of Adobe Creative Suite, bundling its creative software into a single package. The first version of Creative Suite introduced InDesign (the successor to PageMaker), Illustrator, Photoshop, ImageReady and InCopy, with the 2005 second edition of Creative Suite including an updated version of Adobe Acrobat, Premiere Pro, GoLive, the file manager Adobe Bridge, and Adobe Dreamweaver, the latter of which was acquired from a $3.4 billion acquisition of Macromedia, most notably.
In addition to bringing in Dreamweaver, the $3.4 billion Macromedia acquisition, completed as a stock swap, added ColdFusion, Contribute, Captivate, Breeze (rebranded as Adobe Connect), Director, Fireworks, Flash, FlashPaper, Flex, FreeHand, HomeSite, JRun, Presenter, and Authorware to Adobe's product line.
By April 2008, Adobe released Adobe Media Player. On April 27, Adobe discontinued the development and sales of its older HTML/web development software, GoLive, in favor of Dreamweaver. Adobe offered a discount on Dreamweaver for GoLive users and supports those who still use GoLive with online tutorials and migration assistance. On June 1, Adobe launched Acrobat.com, a series of web applications geared for collaborative work. Creative Suite 4, which includes Design, Web, Production Premium, and Master Collection came out in October 2008 in six configurations at prices from about US$1,700 to $2,500 or by individual application. The Windows version of Photoshop includes 64-bit processing.
On December 3, 2008, Adobe laid off 600 of its employees (8% of the worldwide staff) citing the weak economic environment. On September 15, 2009, Adobe Systems announced that it would acquire online marketing and web analytics company Omniture for $1.8 billion. The deal was completed on October 23, 2009. Former Omniture products were integrated into the Adobe Marketing Cloud. On November 10, 2009, the company laid off a further 680 employees.
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Adobe Inc.
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End of Flash, security breach, and employee compensation class action (2010–2014)
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End of Flash, security breach, and employee compensation class action (2010–2014)
right|thumb|Logo of Adobe Systems, 2017–2024
Adobe's 2010 was marked by continuing arguments with Apple over the latter's non-support for Adobe Flash on its iPhone, iPad and other products. Former Apple CEO Steve Jobs claimed that Flash was not reliable or secure enough, while Adobe executives have argued that Apple wishes to maintain control over the iOS platform. In April 2010, Steve Jobs published a post titled Thoughts on Flash where he outlined his thoughts on Flash and the rise of HTML5. In July 2010, Adobe bought Day Software integrating their line of CQ Products: WCM, DAM, SOCO, and Mobile
In January 2011, Adobe acquired DemDex, Inc. with the intent of adding DemDex's audience-optimization software to its online marketing suite. At Photoshop World 2011, Adobe unveiled a new mobile photo service.Darrell Etherington, GigaOm. "Adobe tries mobile photos as a service with Carousel ." September 7, 2011. Retrieved September 12, 2011. Carousel was a new application for iPhone, iPad, and Mac that used Photoshop Lightroom technology to allow users to adjust and fine-tune images on all platforms. Carousel also allowed users to automatically sync, share and browse photos. The service was later renamed "Adobe Revel".John Nack on Adobe: Adobe Carousel renamed "Adobe Revel". Blogs.adobe.com (January 11, 2012). Retrieved on July 21, 2013. Later that same year in October, Adobe acquired Nitobi Software, the maker of the mobile application development framework PhoneGap. As part of the acquisition, the source code of PhoneGap was submitted to the Apache Foundation, where it became Apache Cordova.
In November 2011, Adobe announced that they would cease development of Flash for mobile devices following version 11.1. Instead, it would focus on HTML5 for mobile devices. In December 2011, Adobe announced that it had entered into a definitive agreement to acquire privately held Efficient Frontier. In December 2012, Adobe opened a new corporate campus in Lehi, Utah.
In 2013, Adobe endured a major security breach. Vast portions of the source code for the company's software were stolen and posted online and over 150 million records of Adobe's customers were made readily available for download. In 2012, about 40 million sets of payment card information were compromised by a hack at Adobe.Skimming Off the Top; Why America has such a high rate of payment-card fraud, February 15, 2014, The Economist
A class-action lawsuit alleging that the company suppressed employee compensation was filed against Adobe, and three other Silicon Valley–based companies in a California federal district court in 2013. In May 2014, it was revealed the four companies, Adobe, Apple, Google, and Intel had reached an agreement with the plaintiffs, 64,000 employees of the four companies, to pay a sum of $324.5 million to settle the suit.
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Adobe Inc.
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Adobe Creative Cloud (Since 2011)
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Adobe Creative Cloud (Since 2011)
2011 saw the company first introduce Adobe Creative Cloud, a $600/year subscription plan to its creative software as opposed to a one-time perpetual license payment which could often top $2000 for creative professionals. The initial launch of Creative Cloud alongside Creative Suite 5 users came at the same time that Adobe ran into controversy from users of Adobe's creative software, with users of Adobe software stating that the original perpetual and subscription pricing plans for CS5 would be unaffordable for not only individuals but also businesses, as well as refusing to extend a Creative Suite 6 discount to non-CS5 users. The original announcement of Adobe Creative Cloud was met with a positive reception from CNET journalists as a much more enticing plan, and Creative Cloud was first released in 2012, though a later CNET survey evidenced that more users had a negative perception about subscription creative software than a positive view. The original pricing plan for Creative Cloud was $75 per month for the entire suite of software, though Adobe discounted the monthly cost to $50 for users willing to commit to at least one year of continuous subscription for Creative Cloud, and down to $30 per month for former CS users with the one year commitment.
By 2013, Adobe decided that CS6 would be the last version of Creative Suite software that would be sold through perpetual licensing option, and in May announced that a Creative Cloud subscription would be the only way to get the newest versions of Photoshop, Illustrator, and other Adobe creative software. Reception to the mandatory subscriptions for future Adobe software was mostly negative, despite some positive testimonies on the move from customers and Adobe's attraction of 500,000 Creative Cloud subscribers by the service's first year. The switch to subscription only also did not deter software piracy of Creative Cloud services; within the first day of the first version of Photoshop exclusively made for Creative Cloud being released, cracked versions of Adobe Photoshop CC 2013 were found on The Pirate Bay, an online website used for distributing pirated software.
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Adobe Inc.
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Further acquisitions and failed buyout of Figma (2018–2023)
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Further acquisitions and failed buyout of Figma (2018–2023)
In March 2018, at Adobe Summit, the company and Nvidia announced their association to upgrade their AI and profound learning innovations. They planned to streamline Adobe Sensei AI and machine learning structure for Nvidia GPUs. Adobe and Nvidia had cooperated for 10 years on GPU quickening. This incorporates Sensei-powered features, e.g. auto lip-sync in Adobe Character Animator CC and face-aware editing in Photoshop CC, and also cloud-based AI/ML items and features, for example, picture investigation for Adobe Stock and Lightroom CC and auto-labeling in Adobe Experience Supervisor.
Adobe further spent its time from 2018 to 2023 acquiring more companies to boost both Creative Cloud and the Adobe Experience Cloud, a software suite which increased business. These included e-commerce services provider Magento Commerce from private equity firm Permira for $1.68 billion in June 2018, Marketo for $4.75 billion in 2018, Allegorithmic in 2019 for just under $160 million, and Workfront in December 2020 for $1.5 billion. 2021 additionally saw Adobe add payment services to its e-commerce platforms in an attempt to compete with Shopify, accepting both credit cards and PayPal.
In July 2020, as the United States presidential elections approached, the software giant imposed a ban on the political ads features on its digital advertising sales platform.
On November 9, 2020, Adobe announced it would spend US$1.5 billion to acquire Workfront, a provider of marketing collaboration software. The acquisition was completed in early December 2020.
On August 19, 2021, Adobe announced it had entered into a definitive agreement to acquire Frame.io, a leading cloud-based video collaboration platform. The transaction is valued at $1.275 billion and closed during the fourth quarter of Adobe's 2021 fiscal year.
Adobe announced a $20 billion acquisition of Figma, an Adobe XD competitor, in September 2022, its largest to date. Regulatory scrutiny from the US and European Union began shortly after due to concerns that Adobe, already a major player in the design software market with XD, would have too much control if it also owned Figma. At the time of the announcement to acquire Figma, Adobe's share over the creative software market and design-software market was almost a monopoly. In December 2023, the two companies called off their merger, citing the regulatory challenges as a sign to both that the deal was not likely to be approved. Adobe paid Figma a $1 billion termination fee per their merger agreement.
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Adobe Inc.
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FTC lawsuit and terms of service update (2024–present)
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FTC lawsuit and terms of service update (2024–present)
On June 17, 2024, the US Federal Trade Commission together with the US Department of Justice filed a lawsuit against Adobe for its subscription business model practice, citing hidden termination fees and the company pushing customers towards more expensive plans.
In June 2024, after facing backlash for its changes to the terms of service, Adobe updated them to explicitly pledge it will not use customer data to train its AI models.
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Adobe Inc.
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Products
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Products
Adobe's currently supported roster of software, online services and file formats comprises the following ():
+ Graphic design software Name Icon Type Photoshop x40px Raster graphics editor Photoshop Elements x40px Raster graphics editor, hobbyist Illustrator x40px Vector graphics editor Acrobat DC x40px Portable Document Format viewer, creator, and editor FrameMaker x40px Complex document processor XD x40px Vector design tool for web and mobile applications InDesign x40px Desktop publishing design and typesetting tool InCopy x40px Word processor to edit the textual parts in InDesign layouts. Lightroom x40px Raw image processorExpressx40pxVector design tool for web and mobile applications
+ Web design software Name Icon Type Dreamweaver x40px Web development tool Flash x40px Multimedia software platform
+ Video editing, audio editing, animation, and visual effects software Name Icon Type Premiere Pro x40px Non-linear video editor Premiere Elements x40px Non-linear video editor, hobbyist Audition x40px Audio editor After Effects x40px Digital visual effects, motion graphics, and compositing application Character Animator x40px Motion capture tool Prelude x40px Broadcast ingest and logging application Animate x40px Computer animation application
+ E-learning software Name Icon Type Captivate x40px E-learning course authoring tool Presenter Video Express x40px Screencasting recorder and editor Connect x40px Teleconferencing and videotelephony tool
+ Web design software Name Icon Type ColdFusion x40px Rapid web-application development platform Content Server x40px E-book digital rights management system LiveCycle x40px Java EE Service-oriented architecture software
+ 3D and AR software by Mixamo Name Icon Type Aero x40px Augmented reality authoring and publishing tool Dimension x40px 3D rendering and rudimentary design tool Substance 3D x40px Suite of 3D model and texture authoring tools.
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Adobe Inc.
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Formats
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Formats
Portable Document Format (PDF), PDF's predecessor PostScript, ActionScript, Shockwave Flash (SWF), Flash Video (FLV), and Filmstrip (.flm)
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Adobe Inc.
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Web-hosted services
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Web-hosted services
Adobe Color, Photoshop Express, Acrobat.com, Behance and Adobe Express.
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Adobe Inc.
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Adobe Renderer
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Adobe Renderer
Adobe Media Encoder
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Adobe Inc.
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Adobe Stock
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Adobe Stock
A microstock agency that presently provides over 57 million high-resolution, royalty-free images and videos available to license (via subscription or credit purchase methods). In 2015, Adobe acquired Fotolia, a stock content marketplace founded in 2005 by Thibaud Elziere, Oleg Tscheltzoff, and Patrick Chassany which operated in 23 countries. It was run as a stand-alone website until 2019, but has since been integrated into Adobe Stock.
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Adobe Inc.
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Adobe Experience Platform
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Adobe Experience Platform
A family of content, development, and customer relationship management products, with what Adobe calls the "next generation" of its Sensei artificial intelligence and machine learning framework, introduced in March 2019.
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Adobe Inc.
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Criticisms
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Criticisms
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Adobe Inc.
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Pricing
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Pricing
Adobe has been criticized for its pricing practices, with retail prices being up to twice as much in non-US countries.
After Adobe revealed the pricing for the Creative Suite 3 Master Collection, which was £1,000 higher for European customers, a petition to protest over "unfair pricing" was published and signed by 10,000 users. In June 2009, Adobe further increased its prices in the UK by 10% in spite of weakening of the pound against the dollar, and UK users were not allowed to buy from the US store.
Adobe's Reader and Flash programs were listed on "The 10 most hated programs of all time" article by TechRadar.
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Adobe Inc.
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Security
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Security
Hackers have exploited vulnerabilities in Adobe programs, such as Adobe Reader, to gain unauthorized access to computers. Adobe's Flash Player has also been criticized for, among other things, suffering from performance, memory usage and security problems. A report by security researchers from Kaspersky Lab criticized Adobe for producing the products having top 10 security vulnerabilities.
Observers noted that Adobe was spying on its customers by including spyware in the Creative Suite 3 software and quietly sending user data to a firm named Omniture. When users became aware, Adobe explained what the suspicious software did and admitted that they: "could and should do a better job taking security concerns into account". When a security flaw was later discovered in Photoshop CS5, Adobe sparked outrage by saying it would leave the flaw unpatched, so anyone who wanted to use the software securely would have to pay for an upgrade. Following a fierce backlash Adobe decided to provide the software patch.
Adobe has been criticized for pushing unwanted software including third-party browser toolbars and free virus scanners, usually as part of the Flash update process, and for pushing a third-party scareware program designed to scare users into paying for unneeded system repairs.
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Adobe Inc.
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Customer data breach
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Customer data breach
On October 3, 2013, the company initially revealed that 2.9 million customers' sensitive and personal data was stolen in a security breach which included encrypted credit card information. Adobe later admitted that 38 million active users have been affected and the attackers obtained access to their IDs and encrypted passwords, as well as to many inactive Adobe accounts. The company did not make it clear if all the personal information was encrypted, such as email addresses and physical addresses, though data privacy laws in 44 states require this information to be encrypted.
In late 2013 a 3.8 GB file stolen from Adobe and containing 152 million usernames, reversibly encrypted passwords and unencrypted password hints was posted on AnonNews.org. LastPass, a password security firm, said that Adobe failed to use best practices for securing the passwords and has not salted them. Another security firm, Sophos, showed that Adobe used a weak encryption method permitting the recovery of a lot of information with very little effort. According to IT expert Simon Bain, Adobe has failed its customers and 'should hang their heads in shame'.
Many of the credit cards were tied to the Creative Cloud software-by-subscription service. Adobe offered its affected US customers a free membership in a credit monitoring service, but no similar arrangements have been made for non-US customers. When a data breach occurs in the US, penalties depend on the state where the victim resides, not where the company is based.
After stealing the customers' data, cyber-thieves also accessed Adobe's source code repository, likely in mid-August 2013. Because hackers acquired copies of the source code of Adobe proprietary products, they could find and exploit any potential weaknesses in its security, computer experts warned. Security researcher Alex Holden, chief information security officer of Hold Security, characterized this Adobe breach, which affected Acrobat, ColdFusion and numerous other applications, as "one of the worst in US history". Adobe also announced that hackers stole parts of the source code of Photoshop, which according to commentators could allow programmers to copy its engineering techniques and would make it easier to pirate Adobe's expensive products.
Published on a server of a Russian-speaking hacker group, the "disclosure of encryption algorithms, other security schemes, and software vulnerabilities can be used to bypass protections for individual and corporate data" and may have opened the gateway to new generation zero-day attacks. Hackers already used ColdFusion exploits to make off with usernames and encrypted passwords of PR Newswire's customers, which has been tied to the Adobe security breach. They also used a ColdFusion exploit to breach Washington state court and expose up to 200,000 Social Security numbers.
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Adobe Inc.
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Anti-competitive practices
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Anti-competitive practices
In 1994, Adobe acquired Aldus Corp., a software vendor that sold FreeHand, a competing product. FreeHand was direct competition to Adobe Illustrator, Adobe's flagship vector-graphics editor. The Federal Trade Commission (FTC) intervened and forced Adobe to sell FreeHand back to Altsys, and also banned Adobe from buying back FreeHand or any similar program for the next 10 years (1994–2004). Altsys was then bought by Macromedia, which released versions 5 to 11. When Adobe acquired Macromedia in December 2005, it stalled development of FreeHand in 2007, effectively rendering it obsolete. With FreeHand and Illustrator, Adobe controlled the only two products that compete in the professional illustration program market for Macintosh operating systems.
In 2011, a group of 5,000 FreeHand graphic designers convened under the banner Free FreeHand, and filed a civil antitrust complaint in the US District Court for the Northern District of California against Adobe. The suit alleged that:
Adobe has violated federal and state antitrust laws by abusing its dominant position in the professional vector graphic illustration software market [...] Adobe has engaged in a series of exclusionary and anti-competitive acts and strategies designed to kill FreeHand, the dominant competitor to Adobe's Illustrator software product, instead of competing on the basis of product merit according to the principals of free market capitalism.
Adobe had no response to the claims and the lawsuit was eventually settled. The FreeHand community believes Adobe should release the product to an open-source community if it cannot update it internally.
, on its FreeHand product page, Adobe stated, "While we recognize FreeHand has a loyal customer base, we encourage users to migrate to the new Adobe Illustrator CS4 software which supports both PowerPC and Intel–based Macs and Microsoft Windows XP and Windows Vista." , the FreeHand page no longer exists; instead, it simply redirects to the Illustrator page. Adobe's software FTP server still contains a directory for FreeHand, but it is empty.
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Adobe Inc.
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Cancellation fees
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Cancellation fees
In April 2021, Adobe received criticism from Twitter users for the company's cancellation fees after a customer shared a tweet showing they had been charged a $291.45 cancellation fee for their Adobe Creative Cloud subscription. Many also showed their cancellation fees for Adobe Creative Cloud, with this leading to many encouraging piracy of Adobe products and/or purchase of alternatives with lower prices or using free and open-source software instead. Furthermore, there have been reports that with changing subscriptions it is possible to avoid paying this fee.
The U.S. Department of Justice and the FTC filed a lawsuit against Adobe and two of its executives in June 2024, alleging that the company's deceptive subscription practices and cancellation policies violated the Restore Online Shoppers' Confidence Act. According to the lawsuit, the company purportedly used small text disclosures, optional input fields, and complex web of links to obscure a concealed early termination fee. This fee reportedly amounted to fifty percent of the remaining value of annual contracts for users who chose to cancel early in the first year, resulting in significant penalties. Customers who tried to cancel services by contacting customer service faced obstacles, including dropped calls and multiple transfers between representatives; others continued to be billed by Adobe, under the mistaken belief that they had successfully ended their subscriptions.
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Adobe Inc.
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2024 terms of service update
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2024 terms of service update
On June 5, 2024, Adobe updated their terms of service (TOS) for Photoshop stating "we may access your content through both manual and automated methods, such as for content review." This sparked outrage with Adobe users, as the new terms implied that the users' work would be used to train Adobe's generative AI, even if the work was under a non-disclosure agreement (NDA).
Adobe responded the following day clarifying that they will not use user data to train generative AI or take users work as their own; however, they neglected to respond to the part in the TOS that gives Adobe the ability to view or use work that is contracted under an NDA.
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Adobe Inc.
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See also
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See also
Adobe MAX
Digital rights management (DRM)
List of acquisitions by Adobe
United States v. Elcom Ltd.
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Adobe Inc.
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References
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References
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Adobe Inc.
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External links
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External links
Category:1982 establishments in California
Category:Companies based in San Jose, California
Category:Companies listed on the Nasdaq
Category:Multinational companies headquartered in the United States
Category:Software companies based in the San Francisco Bay Area
Category:Software companies established in 1982
Category:Type foundries
Category:American companies established in 1982
Category:1980s initial public offerings
Category:Software companies of the United States
Category:Audio software companies
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Adobe Inc.
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Table of Content
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Short description, History, PostScript (1982–1986), Introduction of creative software (1986–1996), PDFs and file formats (1993–1999), Creative Suite and the Macromedia acquisition (2000–2009), End of Flash, security breach, and employee compensation class action (2010–2014), Adobe Creative Cloud (Since 2011), Further acquisitions and failed buyout of Figma (2018–2023), FTC lawsuit and terms of service update (2024–present), Products, Formats, Web-hosted services, Adobe Renderer, Adobe Stock, Adobe Experience Platform, Criticisms, Pricing, Security, Customer data breach, Anti-competitive practices, Cancellation fees, 2024 terms of service update, See also, References, External links
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Alexander technique
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short description
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The Alexander technique, named after its developer Frederick Matthias Alexander (1869–1955), is an alternative therapy based on the idea that poor posture causes a range of health problems. The American National Center for Complementary and Integrative Health classifies it as a "psychological and physical" complementary approach to health when used "together with" mainstream conventional medicine.
Alexander began developing his technique's principles in the 1890s to address his own voice loss during public speaking. He credited his method with allowing him to pursue his passion for performing Shakespearean recitations.
Proponents and teachers of the Alexander technique believe the technique can address a variety of health conditions, but there is a lack of research to support the claims. , the UK National Health Service and the National Institute for Health and Care Excellence (NICE) cite evidence that the Alexander technique may be helpful for long-term back pain and for long-term neck pain, and that it could help people cope with Parkinson's disease. Both the American health-insurance company Aetna and the Australian Department of Health have conducted reviews and concluded that there is insufficient evidence for the technique's health claims to warrant insurance coverage.
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Alexander technique
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Method
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Method
The Alexander technique is most commonly taught in a series of private lessons which may last from 30 minutes to an hour. The number of lessons varies widely, depending on the student's needs and level of interest. Students are often performers, such as actors, dancers, musicians, athletes and public speakers, people who work on computers, or those who are in frequent pain for other reasons. Instructors observe their students, and provide both verbal and gentle manual guidance to help students learn how to move with better poise and less strain. Sessions include chair work – often in front of a mirror – during which the instructor will guide the student while the student stands, sits and walks, learning to move efficiently while maintaining a comfortable relationship between the head, neck, and spine, and table work or physical manipulation.
In the United Kingdom, there is no regulation for who can offer Alexander technique services. Professional organisations do exist, however, typically offering three-year courses to people becoming instructors.
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Alexander technique
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History
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History
The Alexander technique is based on the personal observations of Frederick Matthias Alexander (1869–1955). Alexander's career as an actor was hampered by recurrent bouts of laryngitis, but he found he could overcome it by focusing on his discomfort and tension, and relaxing. Alexander also thought posture could be improved if a person became more conscious of their bodily movements.
While on a recital tour in New Zealand (1895), Alexander came to believe in the wider significance of improved carriage for overall physical functioning, although evidence from his own publications appears to indicate it happened less systematically and over a long period of time.
Alexander did not originally conceive of his technique as therapy, but it has become a form of alternative medicine.
When considering how to classify the Alexander technique in relation to mainstream medicine, some sources describe it as alternative and/or complementary, depending on whether it is used alone or with mainstream methods. The American National Center for Complementary and Integrative Health classifies it as a "psychological and physical" complementary approach to health when used with mainstream methods. When used "in place of" conventional medicine, it is considered "alternative".
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Alexander technique
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Influence
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Influence
The American philosopher and educator John Dewey became impressed with the Alexander technique after his headaches, neck pains, blurred vision, and stress symptoms largely improved during the time he used Alexander's advice to change his posture. In 1923, Dewey wrote the introduction to Alexander's Constructive Conscious Control of the Individual.F. M. Alexander, Constructive Conscious Control of the Individual, E. P. Dutton & Co., 1923,
Fritz Perls, who originated Gestalt therapy, credited Alexander as an inspiration for his psychological work.
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Alexander technique
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Uses
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Uses
The Alexander technique is used as a therapy for stress-related chronic conditions. It does not attempt to cure the underlying cause, but to teach people how to avoid bad habits which might exacerbate their condition.
The technique is used as an alternative treatment to improve both voice and posture for people in the performing arts. it was on the curriculum of prominent Western performing arts institutions.
According to Alexander technique instructor Michael J. Gelb, people tend to study the Alexander technique for reasons of personal development.
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Alexander technique
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Health effects
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Health effects
The UK National Health Service says that advocates of the Alexander technique made claims for it that were not supported by evidence, but that there was evidence suggesting that it might help with chronic back or neck pain. According to the NHS, Alexander technique may be of benefit for people with Parkinson disease. The National Institute for Health and Care Excellence (NICE) guidelines state that people with Parkinson disease who are experiencing balance or motor function problems should consider the Alexander technique along with disease-specific physiotherapy. There is limited evidence for chronic pain, stammering, and balance skills in older people. There was no good evidence of benefit for other conditions including asthma, headaches, osteoarthritis, difficulty sleeping, and stress.
A 2012 Cochrane systematic review found that there is no good evidence that the Alexander technique is effective for treating asthma, and randomized clinical trials are needed in order to assess the effectiveness of this type of treatment approach.
A review published in BMC Complementary and Alternative Medicine in 2014 focused on "the evidence for the effectiveness of AT sessions on musicians' performance, anxiety, respiratory function and posture" concluded that "evidence from RCTs and CTs suggests that AT sessions may improve performance anxiety in musicians. Effects on music performance, respiratory function and posture yet remain inconclusive."
A 2015 review, conducted for the Australian Department of Health in order to determine what services the Australian government should pay for, examined clinical trials published to date and found that "overall, the evidence was limited by the small number of participants in the intervention arms, wide confidence intervals or a lack of replication of results." It concluded that "the Alexander technique may improve short-term pain and disability in people with low back pain, but the longer-term effects remain uncertain. For all other clinical conditions, the effectiveness of the Alexander technique was deemed to be uncertain, due to insufficient evidence." It also noted that "evidence for the safety of Alexander Technique was lacking, with most trials not reporting on this outcome." Subsequently, in 2017, the Australian government named the Alexander technique as a practice that would not qualify for insurance subsidy, saying this step would "ensure taxpayer funds are expended appropriately and not directed to therapies lacking evidence".
A review by Aetna last updated in 2021 stated: "Aetna considers the following alternative medicine interventions experimental and investigational because there is inadequate evidence in the peer-reviewed published medical literature of their effectiveness." The Alexander technique is included in that list.
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Alexander technique
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See also
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See also
Nikolai Bernstein
George E. Coghill
Motor skill consolidation
Neutral spine
Psychomotor learning
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Alexander technique
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References
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References
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Alexander technique
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External links
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External links
Category:Mind–body interventions
Category:Postural awareness techniques
Category:Somatics
Category:Alternative medicine
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Alexander technique
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Table of Content
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short description, Method, History, Influence, Uses, Health effects, See also, References, External links
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Andrea Alciato
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short description
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Andrea Alciato (8 May 149212 January 1550), commonly known as Alciati (Andreas Alciatus), was an Italian jurist and writer.D. Bianchi, 1913. "L'opera letteraria e storica di Andrea Alciato", Archivio storico lombardo, 4th series 20:47–57. He is regarded as the founder of the French school of legal humanists.
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Andrea Alciato
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Biography
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Biography
thumb|Engraving of Andrea Alciato
Alciati was born in Alzate Brianza, near Milan, and settled in France in the early 16th century. He displayed great literary skill in his exposition of the laws, and was one of the first to interpret the civil law by the history, languages and literature of antiquity, and to substitute original research for the servile interpretations of the glossators. He published many legal works, and some annotations on Tacitus and accumulated a sylloge of Roman inscriptions from Milan and its territories, as part of his preparation for his history of Milan, written in 1504–05.Roberto Weiss, 1969. The Renaissance Discovery of Antiquity, pp 152f.
Among his several appointments, Alciati taught law at the University of Bourges between 1529 and 1535. It was Guillaume Budé who encouraged the call to Bourges at the time. Pierre Bayle, in his General Dictionary (article "Alciat"), relates that he greatly increased his salary there, by the "stratagem" of arranging to get a job offer from the University of Bologna and using it as a negotiation point .
Alciati is most famous for his Emblemata, published in dozens of editions from 1531 onward. This collection of short Latin verse texts and accompanying woodcuts created an entire European genre, the emblem book, which attained enormous popularity in continental Europe and Great Britain.
Alciati died at Pavia in 1550. His heir, Francesco Alciati, commissioned a huge mausoleum in the Church of S. Epifanio.
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Andrea Alciato
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Works
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Works
right|thumb|Emblem 189: Mentem, non formam, plus pollere ("mind, not outward form, prevails")
Annotationes in tres libros Codicis (1515)
Emblematum libellus (1531)
Opera omnia (Basel 1546–49)
Rerum Patriae, seu Historiae Mediolanensis, Libri IV (Milan, 1625) a history of Milan, written in 1504–05.
De formula Romani Imperii (Basilae: Ioannem Oporinum, 1559, editio princeps)
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Andrea Alciato
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Bibliography
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Bibliography
Andrea Alciato, Il libro degli emblemi secondo le edizioni del 1531 e del 1534, with Introduction, Italian translation and commentary by Mino Gabriele (Milan: Adelphi, 2009; second revised edition 2015) ISBN 978-88-459-2967-0
William S. Heckscher, The Princeton Alciati Companion. A Glossary of Neo-Latin words and phrases used by Andrea Alciati and the emblem book writers of his time, including a bibliography of secondary sources relevant to the study of Alciati's emblems (New York: Garland, 1989) ISBN 0-8240-3715-4
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Andrea Alciato
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Quotation
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Quotation
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Andrea Alciato
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References
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References
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Andrea Alciato
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External links
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External links
Alciato at Glasgow – Reproductions of 22 editions of Alciato's emblems from 1531 to 1621
Description, Reproduction and translation Memorial University of Newfoundland
Emblemata Latin text, Antwerp 1577, full digital facsimile, CAMENA Project
Category:1492 births
Category:1550 deaths
Category:16th-century Italian jurists
Category:16th-century writers in Latin
Category:16th-century Italian historians
Category:16th-century Italian male writers
Category:Italian male non-fiction writers
Category:Italian Renaissance humanists
Category:People from the Province of Como
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Andrea Alciato
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Table of Content
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short description, Biography, Works, Bibliography, Quotation, References, External links
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Apparent magnitude
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Short description
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thumb|upright=1.4|Asteroid 65 Cybele and two stars in the constellation Aquarius, with their magnitudes labeled
Apparent magnitude () is a measure of the brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction of the object's light caused by interstellar dust along the line of sight to the observer.
Unless stated otherwise, the word magnitude in astronomy usually refers to a celestial object's apparent magnitude. The magnitude scale likely dates to before the ancient Roman astronomer Claudius Ptolemy, whose star catalog popularized the system by listing stars from 1st magnitude (brightest) to 6th magnitude (dimmest). The modern scale was mathematically defined to closely match this historical system by Norman Pogson in 1856.
The scale is reverse logarithmic: the brighter an object is, the lower its magnitude number. A difference of 1.0 in magnitude corresponds to the brightness ratio of , or about 2.512. For example, a magnitude 2.0 star is 2.512 times as bright as a magnitude 3.0 star, 6.31 times as magnitude 4.0, and 100 times magnitude 7.0.
The brightest astronomical objects have negative apparent magnitudes: for example, Venus at −4.2 or Sirius at −1.46. The faintest stars visible with the naked eye on the darkest night have apparent magnitudes of about +6.5, though this varies depending on a person's eyesight and with altitude and atmospheric conditions. The apparent magnitudes of known objects range from the Sun at −26.832 to objects in deep Hubble Space Telescope images of magnitude +31.5.
The measurement of apparent magnitude is called photometry. Photometric measurements are made in the ultraviolet, visible, or infrared wavelength bands using standard passband filters belonging to photometric systems such as the UBV system or the Strömgren uvbyβ system. Measurement in the V-band may be referred to as the apparent visual magnitude.
Absolute magnitude is a related quantity which measures the luminosity that a celestial object emits, rather than its apparent brightness when observed, and is expressed on the same reverse logarithmic scale. Absolute magnitude is defined as the apparent magnitude that a star or object would have if it were observed from a distance of . Therefore, it is of greater use in stellar astrophysics since it refers to a property of a star regardless of how close it is to Earth. But in observational astronomy and popular stargazing, references to "magnitude" are understood to mean apparent magnitude.
Amateur astronomers commonly express the darkness of the sky in terms of limiting magnitude, i.e. the apparent magnitude of the faintest star they can see with the naked eye. This can be useful as a way of monitoring the spread of light pollution.
Apparent magnitude is technically a measure of illuminance, which can also be measured in photometric units such as lux.
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Apparent magnitude
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History
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History
Visible totypicalhumaneye Apparentmagnitude Bright-nessrelativeto Vega Number of stars (other than the Sun) brighter thanapparent magnitudein the night sky Yes−1.0 251% 1 (Sirius)0.0 100% 5
(Vega, Canopus, Alpha Centauri,
Arcturus)1.0 40% 152.0 16% 483.0 6.3% 1714.0 2.5% 5135.0 1.0% 6.0 0.4% 6.5 0.25% Bright Star Catalogue No7.0 0.16% 8.0 0.063% 9.0 0.025% 10.0 0.010%
The scale used to indicate magnitude originates in the Hellenistic practice of dividing stars visible to the naked eye into six magnitudes. The brightest stars in the night sky were said to be of first magnitude ( = 1), whereas the faintest were of sixth magnitude ( = 6), which is the limit of human visual perception (without the aid of a telescope). Each grade of magnitude was considered twice the brightness of the following grade (a logarithmic scale), although that ratio was subjective as no photodetectors existed. This rather crude scale for the brightness of stars was popularized by Ptolemy in his Almagest and is generally believed to have originated with Hipparchus. This cannot be proved or disproved because Hipparchus's original star catalogue is lost. The only preserved text by Hipparchus himself (a commentary to Aratus) clearly documents that he did not have a system to describe brightness with numbers: He always uses terms like "big" or "small", "bright" or "faint" or even descriptions such as "visible at full moon".Hoffmann, S., Hipparchs Himmelsglobus, Springer, Wiesbaden/ New York, 2017
In 1856, Norman Robert Pogson formalized the system by defining a first magnitude star as a star that is 100 times as bright as a sixth-magnitude star, thereby establishing the logarithmic scale still in use today. This implies that a star of magnitude is about 2.512 times as bright as a star of magnitude . This figure, the fifth root of 100, became known as . The 1884 Harvard Photometry and 1886 Potsdamer Durchmusterung star catalogs popularized Pogson's ratio, and eventually it became a de facto standard in modern astronomy to describe differences in brightness.
Defining and calibrating what magnitude 0.0 means is difficult, and different types of measurements which detect different kinds of light (possibly by using filters) have different zero points. Pogson's original 1856 paper defined magnitude 6.0 to be the faintest star the unaided eye can see, but the true limit for faintest possible visible star varies depending on the atmosphere and how high a star is in the sky. The Harvard Photometry used an average of 100 stars close to Polaris to define magnitude 5.0. Later, the Johnson UVB photometric system defined multiple types of photometric measurements with different filters, where magnitude 0.0 for each filter is defined to be the average of six stars with the same spectral type as Vega. This was done so the color index of these stars would be 0. Although this system is often called "Vega normalized", Vega is slightly dimmer than the six-star average used to define magnitude 0.0, meaning Vega's magnitude is normalized to 0.03 by definition.
+ Limiting Magnitudes for Visual Observation at High MagnificationTelescopeaperture(mm)LimitingMagnitude 35 11.3 60 12.3 102 13.3 152 14.1 203 14.7 305 15.4 406 15.7 508 16.4
With the modern magnitude systems, brightness is described using Pogson's ratio. In practice, magnitude numbers rarely go above 30 before stars become too faint to detect. While Vega is close to magnitude 0, there are four brighter stars in the night sky at visible wavelengths (and more at infrared wavelengths) as well as the bright planets Venus, Mars, and Jupiter, and since brighter means smaller magnitude, these must be described by negative magnitudes. For example, Sirius, the brightest star of the celestial sphere, has a magnitude of −1.4 in the visible. Negative magnitudes for other very bright astronomical objects can be found in the table below.
Astronomers have developed other photometric zero point systems as alternatives to Vega normalized systems. The most widely used is the AB magnitude system, in which photometric zero points are based on a hypothetical reference spectrum having constant flux per unit frequency interval, rather than using a stellar spectrum or blackbody curve as the reference. The AB magnitude zero point is defined such that an object's AB and Vega-based magnitudes will be approximately equal in the V filter band. However, the AB magnitude system is defined assuming an idealized detector measuring only one wavelength of light, while real detectors accept energy from a range of wavelengths.
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Apparent magnitude
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Measurement
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Measurement
Precision measurement of magnitude (photometry) requires calibration of the photographic or (usually) electronic detection apparatus. This generally involves contemporaneous observation, under identical conditions, of standard stars whose magnitude using that spectral filter is accurately known. Moreover, as the amount of light actually received by a telescope is reduced due to transmission through the Earth's atmosphere, the airmasses of the target and calibration stars must be taken into account. Typically one would observe a few different stars of known magnitude which are sufficiently similar. Calibrator stars close in the sky to the target are favoured (to avoid large differences in the atmospheric paths). If those stars have somewhat different zenith angles (altitudes) then a correction factor as a function of airmass can be derived and applied to the airmass at the target's position. Such calibration obtains the brightness as would be observed from above the atmosphere, where apparent magnitude is defined.
The apparent magnitude scale in astronomy reflects the received power of stars and not their amplitude. Newcomers should consider using the relative brightness measure in astrophotography to adjust exposure times between stars. Apparent magnitude also integrates over the entire object, regardless of its focus, and this needs to be taken into account when scaling exposure times for objects with significant apparent size, like the Sun, Moon and planets. For example, directly scaling the exposure time from the Moon to the Sun works because they are approximately the same size in the sky. However, scaling the exposure from the Moon to Saturn would result in an overexposure if the image of Saturn takes up a smaller area on your sensor than the Moon did (at the same magnification, or more generally, f/#).
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Apparent magnitude
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Calculations
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Calculations
thumb|upright=1.2|Image of 30 Doradus taken by ESO's VISTA. This nebula has a visual magnitude of 8.
thumb|Graph of relative brightness versus magnitude
The dimmer an object appears, the higher the numerical value given to its magnitude, with a difference of 5 magnitudes corresponding to a brightness factor of exactly 100. Therefore, the magnitude , in the spectral band , would be given by
which is more commonly expressed in terms of common (base-10) logarithms as
where is the observed irradiance using spectral filter , and is the reference flux (zero-point) for that photometric filter. Since an increase of 5 magnitudes corresponds to a decrease in brightness by a factor of exactly 100, each magnitude increase implies a decrease in brightness by the factor (Pogson's ratio). Inverting the above formula, a magnitude difference implies a brightness factor of
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Apparent magnitude
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Example: Sun and Moon
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Example: Sun and Moon
What is the ratio in brightness between the Sun and the full Moon?
The apparent magnitude of the Sun is −26.832 (brighter), and the mean magnitude of the full moon is −12.74 (dimmer).
Difference in magnitude:
Brightness factor:
The Sun appears to be approximately times as bright as the full Moon.
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Apparent magnitude
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Magnitude addition
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Magnitude addition
Sometimes one might wish to add brightness. For example, photometry on closely separated double stars may only be able to produce a measurement of their combined light output. To find the combined magnitude of that double star knowing only the magnitudes of the individual components, this can be done by adding the brightness (in linear units) corresponding to each magnitude.
Solving for yields
where is the resulting magnitude after adding the brightnesses referred to by and .
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Apparent magnitude
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Apparent bolometric magnitude
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Apparent bolometric magnitude
While magnitude generally refers to a measurement in a particular filter band corresponding to some range of wavelengths, the apparent or absolute bolometric magnitude (mbol) is a measure of an object's apparent or absolute brightness integrated over all wavelengths of the electromagnetic spectrum (also known as the object's irradiance or power, respectively). The zero point of the apparent bolometric magnitude scale is based on the definition that an apparent bolometric magnitude of 0 mag is equivalent to a received irradiance of 2.518×10−8 watts per square metre (W·m−2).
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Apparent magnitude
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Absolute magnitude
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Absolute magnitude
While apparent magnitude is a measure of the brightness of an object as seen by a particular observer, absolute magnitude is a measure of the intrinsic brightness of an object. Flux decreases with distance according to an inverse-square law, so the apparent magnitude of a star depends on both its absolute brightness and its distance (and any extinction). For example, a star at one distance will have the same apparent magnitude as a star four times as bright at twice that distance. In contrast, the intrinsic brightness of an astronomical object, does not depend on the distance of the observer or any extinction.
The absolute magnitude , of a star or astronomical object is defined as the apparent magnitude it would have as seen from a distance of . The absolute magnitude of the Sun is 4.83 in the V band (visual), 4.68 in the Gaia satellite's G band (green) and 5.48 in the B band (blue).
In the case of a planet or asteroid, the absolute magnitude rather means the apparent magnitude it would have if it were from both the observer and the Sun, and fully illuminated at maximum opposition (a configuration that is only theoretically achievable, with the observer situated on the surface of the Sun).
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Apparent magnitude
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Standard reference values
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Standard reference values
+ Standard apparent magnitudes and fluxes for typical bands Band (μm) (FWHM) Flux at , Jy 10−20 erg/(s·cm2·Hz) U 0.36 0.15 1810 1.81 B 0.44 0.22 4260 4.26 V 0.55 0.16 3640 3.64 R 0.64 0.23 3080 3.08 I 0.79 0.19 2550 2.55 J 1.26 0.16 1600 1.60 H 1.60 0.23 1080 1.08 K 2.22 0.23 670 0.67 L 3.50 g 0.52 0.14 3730 3.73 r 0.67 0.14 4490 4.49 i 0.79 0.16 4760 4.76 z 0.91 0.13 4810 4.81
The magnitude scale is a reverse logarithmic scale. A common misconception is that the logarithmic nature of the scale is because the human eye itself has a logarithmic response. In Pogson's time this was thought to be true (see Weber–Fechner law), but it is now believed that the response is a power law .
Magnitude is complicated by the fact that light is not monochromatic. The sensitivity of a light detector varies according to the wavelength of the light, and the way it varies depends on the type of light detector. For this reason, it is necessary to specify how the magnitude is measured for the value to be meaningful. For this purpose the UBV system is widely used, in which the magnitude is measured in three different wavelength bands: U (centred at about 350 nm, in the near ultraviolet), B (about 435 nm, in the blue region) and V (about 555 nm, in the middle of the human visual range in daylight). The V band was chosen for spectral purposes and gives magnitudes closely corresponding to those seen by the human eye. When an apparent magnitude is discussed without further qualification, the V magnitude is generally understood.
Because cooler stars, such as red giants and red dwarfs, emit little energy in the blue and UV regions of the spectrum, their power is often under-represented by the UBV scale. Indeed, some L and T class stars have an estimated magnitude of well over 100, because they emit extremely little visible light, but are strongest in infrared.
Measures of magnitude need cautious treatment and it is extremely important to measure like with like. On early 20th century and older orthochromatic (blue-sensitive) photographic film, the relative brightnesses of the blue supergiant Rigel and the red supergiant Betelgeuse irregular variable star (at maximum) are reversed compared to what human eyes perceive, because this archaic film is more sensitive to blue light than it is to red light. Magnitudes obtained from this method are known as photographic magnitudes, and are now considered obsolete.
For objects within the Milky Way with a given absolute magnitude, 5 is added to the apparent magnitude for every tenfold increase in the distance to the object. For objects at very great distances (far beyond the Milky Way), this relationship must be adjusted for redshifts and for non-Euclidean distance measures due to general relativity.
For planets and other Solar System bodies, the apparent magnitude is derived from its phase curve and the distances to the Sun and observer.
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Apparent magnitude
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List of apparent magnitudes
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List of apparent magnitudes
Some of the listed magnitudes are approximate. Telescope sensitivity depends on observing time, optical bandpass, and interfering light from scattering and airglow.
+Apparent visual magnitudes of celestial objects Apparentmagnitude(V) Object Seen from...Notes−67.57gamma-ray burst GRB 080319Bseen from 1 AU awaywould be over (20 quadrillion) times as bright as the Sun when seen from the Earth−43.27star NGC 2403 V14seen from 1 AU away−41.82star NGC 2363-V1seen from 1 AU away−41.39star Cygnus OB2-12seen from 1 AU away−40.67star M33-013406.63seen from 1 AU away−40.17star η Carinae Aseen from 1 AU away −40.07 star Zeta1 Scorpii seen from 1 AU away −39.66 star R136a1 seen from 1 AU away−39.47star P Cygniseen from 1 AU away −38.00 star Rigel seen from 1 AU awaywould be seen as a large, very bright bluish disk of 35° apparent diameter−37.42star Betelgeuseseen from 1 AU away −30.30 star Sirius A seen from 1 AU away −29.30 star Sun seen from Mercury at perihelion −27.40 star Sun seen from Venus at perihelion −26.83 star Sun seen from Earthabout 400,000 times as bright as mean full Moon −25.60 star Sun seen from Mars at aphelion −25 Minimum brightness that causes the typical eye slight pain to look at −23.00 star Sun seen from Jupiter at aphelion −21.70 star Sun seen from Saturn at aphelion −21.00 star Sun seen from Earth on an overcast middaymeasuring about 1000 lux −20.20 star Sun seen from Uranus at aphelion −19.30 star Sun seen from Neptune −19.00 star Sun seen from Earth on a very strongly overcast middaymeasuring about 100 lux −18.20 star Sun seen from Pluto at aphelion −17.70 planet Earth seen fully illuminated as earthlight from the Moon −16.70 star Sun seen from Eris at aphelion −16.00 star Sun as twilight on Earthmeasuring about 10 lux −14.2 An illumination level of 1 lux −12.60 full moon seen from Earth at perihelionmaximum brightness of perigee + perihelion + full Moon (~0.267 lux; mean distance value is −12.74, though values are about 0.18 magnitude brighter when including the opposition effect) −12.40 Betelgeuse (when supernova) seen from Earth when it goes supernova −11.20 star Sun seen from Sedna at aphelion −10.00 Comet Ikeya–Seki (1965) seen from Earthwhich was the brightest Kreutz Sungrazer of modern times −9.50Iridium (satellite) flare seen from Earthmaximum brightness −9 to −10 Phobos (moon) seen from Marsmaximum brightness −7.50supernova of 1006 seen from Earththe brightest stellar event in recorded history (7200 light-years away) −6.80Alpha Centauri A seen from Proxima Centauri b −6.00The total integrated magnitude of the night sky (incl. airglow) seen from Earthmeasuring about 0.002 lux −6.00Crab Supernova of 1054 seen from Earth(6500 light-years away) −5.90International Space Station seen from Earthwhen the ISS is at its perigee and fully lit by the Sun −4.92 planet Venus seen from Earthmaximum brightness when illuminated as a crescent −4.14 planet Venus seen from Earthmean brightness −4 Faintest objects observable during the day with naked eye when Sun is high. An astronomical object casts human-visible shadows when its apparent magnitude is equal to or lower than −4 NASA Science Question of the Week. Gsfc.nasa.gov (7 April 2006). Retrieved on 26 April 2013. −3.99 star Epsilon Canis Majoris seen from Earthmaximum brightness of 4.7 million years ago, the historical brightest star of the last and next five million years. – based on computations from HIPPARCOS data. (The calculations exclude stars whose distance or proper motion is uncertain.) −3.69 Moon lit by earthlight, reflecting earthshine seen from Earth (maximum) −2.98 planet Venus seen from Earthminimum brightness during transits. −2.94 planet Jupiter seen from Earthmaximum brightness −2.94 planet Mars seen from Earthmaximum brightness −2.5 Faintest objects visible during the day with naked eye when Sun is less than 10° above the horizon −2.50new moon seen from Earthminimum brightness −2.50 planet Earth seen from Mars maximum brightness −2.48 planet Mercury seen from Earthmaximum brightness at superior conjunction (unlike Venus, Mercury is at its brightest when on the far side of the Sun, the reason being their different phase curves) −2.20 planet Jupiter seen from Earthmean brightness −1.66 planet Jupiter seen from Earthminimum brightness −1.47 star system Sirius seen from EarthBrightest star except for the Sun at visible wavelengths −0.83 star Eta Carinae seen from Earthapparent brightness as a supernova impostor in April 1843 −0.72 star Canopus seen from Earth2nd brightest star in night sky −0.55 planet Saturn seen from Earthmaximum brightness near opposition and perihelion when the rings are angled toward Earth −0.30Halley's comet seen from EarthExpected apparent magnitude at 2061 passage −0.27 star system Alpha Centauri AB seen from EarthCombined magnitude (3rd brightest star in night sky) −0.04 star Arcturus seen from Earth4th brightest star to the naked eye −0.01 star Alpha Centauri A seen from Earth4th brightest individual star visible telescopically in the night sky +0.03 star Vega seen from Earthoriginally chosen as a definition of the zero point +0.23 planet Mercury seen from Earthmean brightness +0.46 star Sun seen from Alpha Centauri +0.46 planet Saturn seen from Earthmean brightness +0.71 planet Mars seen from Earthmean brightness +0.90 Moon seen from Marsmaximum brightness +1.17 planet Saturn seen from Earthminimum brightness +1.33 star Alpha Centauri B seen from Earth +1.86 planet Mars seen from Earthminimum brightness +1.98 star Polaris seen from Earthmean brightness +2.00star system T CrB (when nova)seen from EarthStar system that goes nova every 80 years +2.40Halley's Cometseen from EarthAbout Magnitude during 1986 perihelion +3 Faintest objects visible in an urban neighborhood with naked eye +3.03 supernova SN 1987A seen from Earthin the Large Magellanic Cloud (160,000 light-years away) +3.44Andromeda Galaxy seen from EarthM31 +4 Faintest objects visible in an urban neighborhood with naked eye +4.00Orion Nebula seen from EarthM42 +4.38 moon Ganymede seen from Earthmaximum brightness (moon of Jupiter and the largest moon in the Solar System) +4.50 open cluster M41 seen from Earthan open cluster that may have been seen by Aristotle +4.50Sagittarius Dwarf Spheroidal Galaxyseen from Earth +5.20 asteroid Vesta seen from Earthmaximum brightness +5.38 planet Uranus seen from Earthmaximum brightness (Uranus comes to perihelion in 2050) +5.68 planet Uranus seen from Earthmean brightness +5.72 spiral galaxy M33 seen from Earthwhich is used as a test for naked eye seeing under dark skies (Shows bolometric magnitude not visual magnitude.) +5.80 gamma-ray burst GRB 080319B seen from EarthPeak visual magnitude (the "Clarke Event") seen on Earth on 19 March 2008 from a distance of 7.5 billion light-years. +6.03 planet Uranus seen from Earthminimum brightness +6.49 asteroid Pallas seen from Earthmaximum brightness +6.5 Approximate limit of stars observed by a mean naked eye observer under very good conditions. There are about 9,500 stars visible to mag 6.5. +6.50 global cluster M2 seen from Earthmean naked-eye target +6.64 dwarf planet Ceres seen from Earthmaximum brightness +6.75 asteroid Iris seen from Earthmaximum brightness +6.90 spiral galaxy M81 seen from EarthThis is an extreme naked-eye target that pushes human eyesight and the Bortle scale to the limit +7.25 planet Mercury seen from Earthminimum brightness +7.67 planet Neptune seen from Earthmaximum brightness (Neptune comes to perihelion in 2042) +7.78 planet Neptune seen from Earthmean brightness +8Extreme naked-eye limit, Class 1 on Bortle scale, the darkest skies available on Earth. +8.00 planet Neptune seen from Earthminimum brightness +8.10 moon Titan seen from Earthmaximum brightness; largest moon of Saturn; mean opposition magnitude 8.4 +8.29star UY Scutiseen from EarthMaximum brightness; one of largest known stars by radius +8.94 asteroid 10 Hygiea seen from Earthmaximum brightness +9.30 spiral galaxy M63 seen from Earth +9.5Faintest objects visible using common 10×50 binoculars under typical conditions +10 Apollo 8 CSM in orbit around the Moon seen from Earthcalculated (Liemohn) +10star system T CrB(average)seen from EarthStar system that goes nova every 80 years +10.20 moon Iapetus seen from Earthmaximum brightness, brightest when west of Saturn and takes 40 days to switch sides +11.05star Proxima Centauriseen from Earthclosest star (other than the Sun) +11.8moon Phobosseen from EarthMaximum brightness; brighter moon of Mars +12.23star R136a1seen from EarthMost luminous and massive star known +12.89moon Deimosseen from EarthMaximum brightness +12.91quasar 3C 273 seen from Earthbrightest (luminosity distance of 2.4 billion light-years) +13.42 moon Triton seen from EarthMaximum brightness +13.65 dwarf planet Pluto seen from Earthmaximum brightness, 725 times fainter than magnitude 6.5 naked eye skies +13.9moon Titaniaseen from EarthMaximum brightness; brightest moon of Uranus +14.1star WR 102seen from EarthHottest known star +15.4 centaur Chiron seen from Earthmaximum brightness +15.55 moon Charon seen from Earthmaximum brightness (the largest moon of Pluto) +16.8 dwarf planet Makemake seen from EarthCurrent opposition brightness +17.27 dwarf planet Haumea seen from EarthCurrent opposition brightness +18.7 dwarf planet Eris seen from EarthCurrent opposition brightness +19.5 Faintest objects observable with the Catalina Sky Survey 0.7-meter telescope using a 30-second exposure and also the approximate limiting magnitude of Asteroid Terrestrial-impact Last Alert System (ATLAS) +20.7 moon Callirrhoe seen from Earth(small ≈8 km satellite of Jupiter) +22 Faintest objects observable in visible light with a 600 mm (24″) Ritchey-Chrétien telescope with 30 minutes of stacked images (6 subframes at 5 minutes each) using a CCD detector +22.8Luhman 16seen from EarthClosest brown dwarfs (Luhman 16A=23.25, Luhman 16B=24.07) +22.91 moon Hydra seen from Earthmaximum brightness of Pluto's moon +23.38 moon Nix seen from Earthmaximum brightness of Pluto's moon +24 Faintest objects observable with the Pan-STARRS 1.8-meter telescope using a 60-second exposure This is currently the limiting magnitude of automated allsky astronomical surveys. +25.0 moon Fenrir seen from Earth(small ≈4 km satellite of Saturn) and about 25 million times fainter than what can be seen with the naked eye. +25.3 Trans-Neptunian object seen from EarthFurthest known observable object in the Solar System about from the Sun +26.2 Trans-Neptunian object seen from Earth200 km sized object about from the Sun and about 75 million times fainter than what can be seen with the naked eye. +27.7 Faintest objects observable with a single 8-meter class ground-based telescope such as the Subaru Telescope in a 10-hour imageWhat is the faintest object imaged by ground-based telescopes? , by: The Editors of Sky Telescope, 24 July 2006 +28.2 Halley's Comet seen from Earth (2003)in 2003 when it was from the Sun, imaged using 3 of 4 synchronised individual scopes in the ESO's Very Large Telescope array using a total exposure time of about 9 hours +28.4 asteroid seen from Earth orbitobserved magnitude of ≈15-kilometer Kuiper belt object seen by the Hubble Space Telescope (HST) in 2003, dimmest known directly observed asteroid. +29.4 JADES-GS-z13-0 seen from Earth Discovered by the James Webb Space Telescope. One of the furthest objects discovered. Approximately a billion times fainter than can be observed with the naked eye. +31.5 Faintest objects observable in visible light with Hubble Space Telescope via the EXtreme Deep Field with ≈23 days of exposure time collected over 10 years +35 unnamed asteroid seen from Earth orbitexpected magnitude of dimmest known asteroid, a 950-meter Kuiper belt object discovered (by the HST) passing in front of a star in 2009. +35 star LBV 1806−20 seen from Eartha luminous blue variable star, expected magnitude at visible wavelengths due to interstellar extinction
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Apparent magnitude
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See also
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See also
Angular diameter
Distance modulus
List of nearest bright stars
List of nearest stars
Luminosity
Surface brightness
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Apparent magnitude
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References
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References
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Apparent magnitude
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External links
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External links
Category:Observational astronomy
Category:Logarithmic scales of measurement
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Apparent magnitude
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Table of Content
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Short description, History, Measurement, Calculations, Example: Sun and Moon, Magnitude addition, Apparent bolometric magnitude, Absolute magnitude, Standard reference values, List of apparent magnitudes, See also, References, External links
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Absolute magnitude
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Short description
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In astronomy, absolute magnitude () is a measure of the luminosity of a celestial object on an inverse logarithmic astronomical magnitude scale; the more luminous (intrinsically bright) an object, the lower its magnitude number. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it were viewed from a distance of exactly , without extinction (or dimming) of its light due to absorption by interstellar matter and cosmic dust. By hypothetically placing all objects at a standard reference distance from the observer, their luminosities can be directly compared among each other on a magnitude scale. For Solar System bodies that shine in reflected light, a different definition of absolute magnitude (H) is used, based on a standard reference distance of one astronomical unit.
Absolute magnitudes of stars generally range from approximately −10 to +20. The absolute magnitudes of galaxies can be much lower (brighter).
The more luminous an object, the smaller the numerical value of its absolute magnitude. A difference of 5 magnitudes between the absolute magnitudes of two objects corresponds to a ratio of 100 in their luminosities, and a difference of n magnitudes in absolute magnitude corresponds to a luminosity ratio of 100n/5. For example, a star of absolute magnitude MV = 3.0 would be 100 times as luminous as a star of absolute magnitude MV = 8.0 as measured in the V filter band. The Sun has absolute magnitude MV = +4.83. Highly luminous objects can have negative absolute magnitudes: for example, the Milky Way galaxy has an absolute B magnitude of about −20.8.
As with all astronomical magnitudes, the absolute magnitude can be specified for different wavelength ranges corresponding to specified filter bands or passbands; for stars a commonly quoted absolute magnitude is the absolute visual magnitude, which uses the visual (V) band of the spectrum (in the UBV photometric system). Absolute magnitudes are denoted by a capital M, with a subscript representing the filter band used for measurement, such as MV for absolute magnitude in the V band.
An object's absolute bolometric magnitude (Mbol) represents its total luminosity over all wavelengths, rather than in a single filter band, as expressed on a logarithmic magnitude scale. To convert from an absolute magnitude in a specific filter band to absolute bolometric magnitude, a bolometric correction (BC) is applied.
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Absolute magnitude
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Stars and galaxies
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Stars and galaxies
In stellar and galactic astronomy, the standard distance is 10 parsecs (about 32.616 light-years, 308.57 petameters or 308.57 trillion kilometres). A star at 10 parsecs has a parallax of 0.1″ (100 milliarcseconds). Galaxies (and other extended objects) are much larger than 10 parsecs; their light is radiated over an extended patch of sky, and their overall brightness cannot be directly observed from relatively short distances, but the same convention is used. A galaxy's magnitude is defined by measuring all the light radiated over the entire object, treating that integrated brightness as the brightness of a single point-like or star-like source, and computing the magnitude of that point-like source as it would appear if observed at the standard 10 parsecs distance. Consequently, the absolute magnitude of any object equals the apparent magnitude it would have if it were 10 parsecs away.
Some stars visible to the naked eye have such a low absolute magnitude that they would appear bright enough to outshine the planets and cast shadows if they were at 10 parsecs from the Earth. Examples include Rigel (−7.8), Deneb (−8.4), Naos (−6.2), and Betelgeuse (−5.8). For comparison, Sirius has an absolute magnitude of only 1.4, which is still brighter than the Sun, whose absolute visual magnitude is 4.83. The Sun's absolute bolometric magnitude is set arbitrarily, usually at 4.75.
Absolute magnitudes of stars generally range from approximately −10 to +20. The absolute magnitudes of galaxies can be much lower (brighter). For example, the giant elliptical galaxy M87 has an absolute magnitude of −22 (i.e. as bright as about 60,000 stars of magnitude −10). Some active galactic nuclei (quasars like CTA-102) can reach absolute magnitudes in excess of −32, making them the most luminous persistent objects in the observable universe, although these objects can vary in brightness over astronomically short timescales. At the extreme end, the optical afterglow of the gamma ray burst GRB 080319B reached, according to one paper, an absolute r magnitude brighter than −38 for a few tens of seconds.
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Absolute magnitude
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Apparent magnitude
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Apparent magnitude
The Greek astronomer Hipparchus established a numerical scale to describe the brightness of each star appearing in the sky. The brightest stars in the sky were assigned an apparent magnitude , and the dimmest stars visible to the naked eye are assigned . The difference between them corresponds to a factor of 100 in brightness. For objects within the immediate neighborhood of the Sun, the absolute magnitude and apparent magnitude from any distance (in parsecs, with 1 pc = 3.2616 light-years) are related by
where is the radiant flux measured at distance (in parsecs), the radiant flux measured at distance . Using the common logarithm, the equation can be written as
where it is assumed that extinction from gas and dust is negligible. Typical extinction rates within the Milky Way galaxy are 1 to 2 magnitudes per kiloparsec, when dark clouds are taken into account.
For objects at very large distances (outside the Milky Way) the luminosity distance (distance defined using luminosity measurements) must be used instead of , because the Euclidean approximation is invalid for distant objects. Instead, general relativity must be taken into account. Moreover, the cosmological redshift complicates the relationship between absolute and apparent magnitude, because the radiation observed was shifted into the red range of the spectrum. To compare the magnitudes of very distant objects with those of local objects, a K correction might have to be applied to the magnitudes of the distant objects.
The absolute magnitude can also be written in terms of the apparent magnitude and stellar parallax :
or using apparent magnitude and distance modulus :
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Absolute magnitude
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Examples
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Examples
Rigel has a visual magnitude of 0.12 and distance of about 860 light-years:
Vega has a parallax of 0.129″, and an apparent magnitude of 0.03:
The Black Eye Galaxy has a visual magnitude of 9.36 and a distance modulus of 31.06:
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Absolute magnitude
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Bolometric magnitude
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Bolometric magnitude
The absolute bolometric magnitude () takes into account electromagnetic radiation at all wavelengths. It includes those unobserved due to instrumental passband, the Earth's atmospheric absorption, and extinction by interstellar dust. It is defined based on the luminosity of the stars. In the case of stars with few observations, it must be computed assuming an effective temperature.
Classically, the difference in bolometric magnitude is related to the luminosity ratio according to:
which makes by inversion:
where
is the Sun's luminosity (bolometric luminosity)
is the star's luminosity (bolometric luminosity)
is the bolometric magnitude of the Sun
is the bolometric magnitude of the star.
In August 2015, the International Astronomical Union passed Resolution B2 defining the zero points of the absolute and apparent bolometric magnitude scales in SI units for power (watts) and irradiance (W/m2), respectively. Although bolometric magnitudes had been used by astronomers for many decades, there had been systematic differences in the absolute magnitude-luminosity scales presented in various astronomical references, and no international standardization. This led to systematic differences in bolometric corrections scales. Combined with incorrect assumed absolute bolometric magnitudes for the Sun, this could lead to systematic errors in estimated stellar luminosities (and other stellar properties, such as radii or ages, which rely on stellar luminosity to be calculated).
Resolution B2 defines an absolute bolometric magnitude scale where corresponds to luminosity , with the zero point luminosity set such that the Sun (with nominal luminosity ) corresponds to absolute bolometric magnitude . Placing a radiation source (e.g. star) at the standard distance of 10 parsecs, it follows that the zero point of the apparent bolometric magnitude scale corresponds to irradiance . Using the IAU 2015 scale, the nominal total solar irradiance ("solar constant") measured at 1 astronomical unit () corresponds to an apparent bolometric magnitude of the Sun of .
Following Resolution B2, the relation between a star's absolute bolometric magnitude and its luminosity is no longer directly tied to the Sun's (variable) luminosity:
where
is the star's luminosity (bolometric luminosity) in watts
is the zero point luminosity
is the bolometric magnitude of the star
The new IAU absolute magnitude scale permanently disconnects the scale from the variable Sun. However, on this SI power scale, the nominal solar luminosity corresponds closely to , a value that was commonly adopted by astronomers before the 2015 IAU resolution.
The luminosity of the star in watts can be calculated as a function of its absolute bolometric magnitude as:
using the variables as defined previously.
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Absolute magnitude
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Solar System bodies ({{mvar
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Solar System bodies ()
+ Abs Mag (H)and Diameterfor asteroids(albedo=0.14)CNEOS Asteroid Size Estimator H Diameter 10 36 km 12.7 10 km 15 3.6 km 17.7 1 km 19.2 510 m 20 360 m 22 140 m 22.7 100 m 24.2 51 m 25 36 m 26.6 17 m 27.7 10 m 30 3.6 m 32.7 1 m
For planets and asteroids, a definition of absolute magnitude that is more meaningful for non-stellar objects is used. The absolute magnitude, commonly called , is defined as the apparent magnitude that the object would have if it were one astronomical unit (AU) from both the Sun and the observer, and in conditions of ideal solar opposition (an arrangement that is impossible in practice). Because Solar System bodies are illuminated by the Sun, their brightness varies as a function of illumination conditions, described by the phase angle. This relationship is referred to as the phase curve. The absolute magnitude is the brightness at phase angle zero, an arrangement known as opposition, from a distance of one AU.
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Absolute magnitude
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Apparent magnitude
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Apparent magnitude
thumb|right|250px|The phase angle can be calculated from the distances body-sun, observer-sun and observer-body, using the law of cosines.
The absolute magnitude can be used to calculate the apparent magnitude of a body. For an object reflecting sunlight, and are connected by the relation
where is the phase angle, the angle between the body-Sun and body–observer lines. is the phase integral (the integration of reflected light; a number in the 0 to 1 range).
By the law of cosines, we have:
Distances:
is the distance between the body and the observer
is the distance between the body and the Sun
is the distance between the observer and the Sun
, a unit conversion factor, is the constant 1 AU, the average distance between the Earth and the Sun
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Absolute magnitude
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Approximations for phase integral {{serif
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Approximations for phase integral
The value of depends on the properties of the reflecting surface, in particular on its roughness. In practice, different approximations are used based on the known or assumed properties of the surface. The surfaces of terrestrial planets are generally more difficult to model than those of gaseous planets, the latter of which have smoother visible surfaces.
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Absolute magnitude
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Planets as diffuse spheres
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Planets as diffuse spheres
thumb|right|240px|Diffuse reflection on sphere and flat disk
thumb|240px|Brightness with phase for diffuse reflection models. The sphere is 2/3 as bright at zero phase, while the disk can't be seen beyond 90 degrees.
Planetary bodies can be approximated reasonably well as ideal diffuse reflecting spheres. Let be the phase angle in degrees, then
A full-phase diffuse sphere reflects two-thirds as much light as a diffuse flat disk of the same diameter. A quarter phase () has as much light as full phase ().
By contrast, a diffuse disk reflector model is simply , which isn't realistic, but it does represent the opposition surge for rough surfaces that reflect more uniform light back at low phase angles.
The definition of the geometric albedo , a measure for the reflectivity of planetary surfaces, is based on the diffuse disk reflector model. The absolute magnitude , diameter (in kilometers) and geometric albedo of a body are related by
or equivalently,
Example: The Moon's absolute magnitude can be calculated from its diameter and geometric albedo :
We have ,
At quarter phase, (according to the diffuse reflector model), this yields an apparent magnitude of The actual value is somewhat lower than that, This is not a good approximation, because the phase curve of the Moon is too complicated for the diffuse reflector model. A more accurate formula is given in the following section.
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Absolute magnitude
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More advanced models
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More advanced models
Because Solar System bodies are never perfect diffuse reflectors, astronomers use different models to predict apparent magnitudes based on known or assumed properties of the body. For planets, approximations for the correction term in the formula for have been derived empirically, to match observations at different phase angles. The approximations recommended by the Astronomical Almanac are (with in degrees):
Planet Referenced calculation Approximation for Mercury −0.4 −0.613 Venus −4.4 −4.384 (for )
(for ) Earth − −3.99 Moon 0.2 +0.28 (for , before full Moon)
(for , after full Moon) Mars −1.5 −1.601 (for )
(for ) Jupiter −9.4 −9.395 (for )
(for ) Saturn −9.7 −8.914 (for planet and rings, and )
(for the globe alone, )
(for the globe alone, ) Uranus −7.2 −7.110 (for ) Neptune −6.9 −7.00 (for and )
Here is the effective inclination of Saturn's rings (their tilt relative to the observer), which as seen from Earth varies between 0° and 27° over the course of one Saturn orbit, and is a small correction term depending on Uranus' sub-Earth and sub-solar latitudes. is the Common Era year. Neptune's absolute magnitude is changing slowly due to seasonal effects as the planet moves along its 165-year orbit around the Sun, and the approximation above is only valid after the year 2000. For some circumstances, like for Venus, no observations are available, and the phase curve is unknown in those cases. The formula for the Moon is only applicable to the near side of the Moon, the portion that is visible from the Earth.
Example 1: On 1 January 2019, Venus was from the Sun, and from Earth, at a phase angle of (near quarter phase). Under full-phase conditions, Venus would have been visible at Accounting for the high phase angle, the correction term above yields an actual apparent magnitude of This is close to the value of predicted by the Jet Propulsion Laboratory.
Example 2: At first quarter phase, the approximation for the Moon gives With that, the apparent magnitude of the Moon is close to the expected value of about . At last quarter, the Moon is about 0.06 mag fainter than at first quarter, because that part of its surface has a lower albedo.
Earth's albedo varies by a factor of 6, from 0.12 in the cloud-free case to 0.76 in the case of altostratus cloud. The absolute magnitude in the table corresponds to an albedo of 0.434. Due to the variability of the weather, Earth's apparent magnitude cannot be predicted as accurately as that of most other planets.
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Absolute magnitude
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Asteroids
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Asteroids
thumb|right|240px|Asteroid 1 Ceres, imaged by the Dawn spacecraft at phase angles of 0°, 7° and 33°. The strong difference in brightness between the three is real. The left image at 0° phase angle shows the brightness surge due to the opposition effect.
thumb|240px|Phase integrals for various values of G
thumb|right|240px|Relationship between the slope parameter and the opposition surge. Larger values of correspond to a less pronounced opposition effect. For most asteroids, a value of is assumed, corresponding to an opposition surge of .
If an object has an atmosphere, it reflects light more or less isotropically in all directions, and its brightness can be modelled as a diffuse reflector. Bodies with no atmosphere, like asteroids or moons, tend to reflect light more strongly to the direction of the incident light, and their brightness increases rapidly as the phase angle approaches . This rapid brightening near opposition is called the opposition effect. Its strength depends on the physical properties of the body's surface, and hence it differs from asteroid to asteroid.
In 1985, the IAU adopted the semi-empirical -system, based on two parameters and called absolute magnitude and slope, to model the opposition effect for the ephemerides published by the Minor Planet Center.
where
the phase integral is and
for or , , , and .
This relation is valid for phase angles , and works best when .
The slope parameter relates to the surge in brightness, typically , when the object is near opposition. It is known accurately only for a small number of asteroids, hence for most asteroids a value of is assumed. In rare cases, can be negative. An example is 101955 Bennu, with .
In 2012, the -system was officially replaced by an improved system with three parameters , and , which produces more satisfactory results if the opposition effect is very small or restricted to very small phase angles. However, as of 2022, this -system has not been adopted by either the Minor Planet Center nor Jet Propulsion Laboratory.
The apparent magnitude of asteroids varies as they rotate, on time scales of seconds to weeks depending on their rotation period, by up to or more. In addition, their absolute magnitude can vary with the viewing direction, depending on their axial tilt. In many cases, neither the rotation period nor the axial tilt are known, limiting the predictability. The models presented here do not capture those effects.
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Absolute magnitude
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Cometary magnitudes
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Cometary magnitudes
The brightness of comets is given separately as total magnitude (, the brightness integrated over the entire visible extend of the coma) and nuclear magnitude (, the brightness of the core region alone). Both are different scales than the magnitude scale used for planets and asteroids, and can not be used for a size comparison with an asteroid's absolute magnitude .
The activity of comets varies with their distance from the Sun. Their brightness can be approximated as
where are the total and nuclear apparent magnitudes of the comet, respectively, are its "absolute" total and nuclear magnitudes, and are the body-sun and body-observer distances, is the Astronomical Unit, and are the slope parameters characterising the comet's activity. For , this reduces to the formula for a purely reflecting body (showing no cometary activity).
For example, the lightcurve of comet C/2011 L4 (PANSTARRS) can be approximated by On the day of its perihelion passage, 10 March 2013, comet PANSTARRS was from the Sun and from Earth. The total apparent magnitude is predicted to have been at that time. The Minor Planet Center gives a value close to that, .
+Absolute magnitudes and sizes of comet nuclei Comet Absolutemagnitude NucleusdiameterComet Sarabat −3.0 ≈100 km?Comet Hale-Bopp −1.3 60 ± 20 kmComet Halley 4.0 14.9 x 8.2 kmaverage new comet 6.5 ≈2 kmC/2014 UN271 (Bernardinelli-Bernstein) 6.7 60–200 km?289P/Blanpain (during 1819 outburst) 8.5 320 m289P/Blanpain (normal activity) 22.9 320 m
The absolute magnitude of any given comet can vary dramatically. It can change as the comet becomes more or less active over time or if it undergoes an outburst. This makes it difficult to use the absolute magnitude for a size estimate. When comet 289P/Blanpain was discovered in 1819, its absolute magnitude was estimated as . It was subsequently lost and was only rediscovered in 2003. At that time, its absolute magnitude had decreased to , and it was realised that the 1819 apparition coincided with an outburst. 289P/Blanpain reached naked eye brightness (5–8 mag) in 1819, even though it is the comet with the smallest nucleus that has ever been physically characterised, and usually doesn't become brighter than 18 mag.
For some comets that have been observed at heliocentric distances large enough to distinguish between light reflected from the coma, and light from the nucleus itself, an absolute magnitude analogous to that used for asteroids has been calculated, allowing to estimate the sizes of their nuclei.
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Absolute magnitude
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Meteors
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Meteors
For a meteor, the standard distance for measurement of magnitudes is at an altitude of at the observer's zenith.
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Absolute magnitude
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See also
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See also
Araucaria Project
Hertzsprung–Russell diagram – relates absolute magnitude or luminosity versus spectral color or surface temperature.
Jansky - the preferred unit for radio astronomy – linear in power/unit area
List of most luminous stars
Photographic magnitude
Surface brightness – the magnitude for extended objects
Zero point (photometry) – the typical calibration point for star flux
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Absolute magnitude
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References
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References
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