text: '''
  Helper functions to download data for tutorials.
  '''
  
  from astropy.utils.data import download_file
  from astropy.io import ascii
  from astropy.table import Table
  from astroquery.gaia import Gaia
  
  def get_confirmed_planets(cache=True, show_progress=True,
                              select=None):
      """
      Download (and optionally cache) a table from the `NExScI Exoplanet Archive 
                                  <http://exoplanetarchive.ipac.caltech.edu/index.html>`_.
      Based on the code from `astroquery <https://github.com/astropy/astroquery>`_.
                                  
      Parameters
      ----------
      cache : bool (optional)
          Cache table to local astropy cache? Default is `True`.
      show_progress : bool (optional)
          Show progress of table download (if no cached copy is
          available). Default is `True`.
      select : str (optional)
          Comma-separated, no spaces string indicating columns to be
          returned. Default `None` will select all default columns
          as set by the Exoplanet Archive API. `*` will select all.
      Returns
      -------
      table : `~astropy.table`
          Astropy table of requested data.
      """
      url = 'http://exoplanetarchive.ipac.caltech.edu/cgi-bin/nstedAPI/nph-nstedAPI?table=exoplanets'
      url += '&format=csv'
      if not select is None:
          url += '&select='+select
      table_path = download_file(url, cache=cache,
                                     show_progress=show_progress,
                                     timeout=120)
      table = ascii.read(table_path)
      
      # Store column of planet names:
      pl_names = [host_name.replace(' ', '') + letter
                         for host_name, letter in
                         zip(table['pl_hostname'].data,
                             table['pl_letter'].data)]
      table['pl_name'] = pl_names
      
      return table
      
  def get_cepheids():
      """
      Execute ADQL query for Gaia DR1 Cepheids using astroquery's TAP+ utils.
      
      Returns
      -------
      table : `~astropy.table`
          Astropy table of requested data.
      """
      job = Gaia.launch_job("SELECT cep.*, gaia.ra, gaia.dec \
          FROM gaiadr1.cepheid AS cep \
          INNER JOIN gaiadr1.gaia_source as gaia \
          on cep.source_id = gaia.source_id")
      return job.get_results()