Open astronomy tools

Angular separation (deg, arcmin, arcsec) and position angle (from north through east) between two points, plus the east/north offset in arcseconds.

Light-travel-time (to BJD_TDB or HJD_TDB) and radial-velocity correction (km/s, to add to the observed velocity) for a target at an observatory, using astropy's built-in ephemeris (no download).

Best nights to observe a field over a date range (up to 366 nights): per night the dark hours, hours the target is above a minimum altitude in the dark with the Moon far enough or down, Moon illumination; returns the top nights.

Convert a position between ICRS, FK5 (J2000), FK4 (B1950), Galactic, ecliptic (J2000) and supergalactic, and between sexagesimal and degrees. A string right ascension is HOURS ('18h36m56.3s', '18:36:56.3'); numbers are degrees. Returns the target frame plus ICRS, Galactic and ecliptic for reference.

Convert times between UTC, TAI, TT, TDB and UT1 and between ISO, JD, MJD, Unix and decimal years. Returns UTC/TAI/TT/TDB, JD and MJD, TT-UTC and UT1-UTC. 1900-2100, up to 200 times.

Convert a value between astronomical/physical units (astropy), with optional equivalencies: 'spectral' (wavelength/frequency/energy), 'spectral_density' (F_nu/F_lambda at a wavelength), 'parallax', 'temperature', Doppler.

Redshift and distance in a selectable cosmology (Planck18 default; planck15, planck13, wmap9, or a custom flat/open one from h0, om0, ode0): comoving, luminosity and angular-diameter distances, distance modulus, lookback time, age, proper scale (kpc/arcsec); optionally the absolute magnitude (NO K-correction) and luminosity. Or solve z from a luminosity distance.

A(lambda)/A(V) and A(lambda) from the Cardelli-Clayton-Mathis (1989) extinction law for a given E(B-V) and R_V (default 3.1), 1000-33333 Angstrom. The dust column along a sightline is YOUR input: this package bundles no dust map (no offline map is available), so it cannot look up E(B-V) for a position.

Which of a list of targets (up to 2000) fall inside a circular field around a centre, of a radius you give: separation, position angle and east/north offsets. A first-cut membership test, not a fibre or detector configuration.

The observatories bundled for planning (La Palma WHT/INT/GTC, Paranal, Cerro Pachon, Siding Spring) with latitude, longitude (east positive) and height.

Magnitude and flux density in the AB, ST or Vega system (Vega bands U B V R I J H Ks bundled). Returns Jy, mJy, uJy, erg/s/cm2/Hz and, with a wavelength, erg/s/cm2/Angstrom.

The timeline of a night at an observatory: sunset, civil/nautical/astronomical twilight (evening and morning), night length, local sidereal time at start/mid/end, moonrise, moonset and Moon illumination. Times UTC (optionally also a fixed local offset).

Move a star's ICRS position from one epoch to another using its proper motion (mas/yr; pmra is mu_alpha* = includes cos dec, as in Gaia) and optionally parallax and radial velocity. Epochs: a Julian year (2016.0 or 'J2016.0', the Gaia DR3 epoch) or an ISO date.

z and velocity (relativistic Doppler and cz) and rest and observed wavelength: give z, or a velocity, or rest and observed wavelengths; with only one wavelength it computes the other.

Local and Greenwich sidereal time (mean and apparent) at an observatory for given UTC times.

Look up standard spectral lines from a small bundled table (hydrogen Lyman/Balmer/Paschen/Brackett, [OII], [OIII], [NII], [SII], [OI], He I/II, Ca II H&K and triplet, Mg b, Na D, UV lines): vacuum and air rest wavelengths, shifted by a redshift or velocity, optionally only those landing in an observed wavelength window.

Visibility of up to 20 targets over one night at an observatory: altitude, azimuth, airmass and Moon separation every N minutes, maximum altitude and when, hours above a minimum altitude, first/last time above it, and a warning near a bright Moon. Geometric altitudes, Pickering airmass.

The papers that CITE one paper, from ADS (use year_from for recent ones, sort 'date desc' for the newest first).

Full ADS record of one paper by bibcode: abstract, all metadata, keywords, citation and read counts, links, provenance.

List the ADS libraries (reading lists) of the ADS account that owns your token. Read-only.

Read the papers of one ADS library by its id (the code in the library's ADS address), with their metadata. Read-only; 50 papers per page.

What has been written about an astronomical object: ADS papers that mention it (name resolved through SIMBAD/NED by ADS), refereed by default, most cited first. Use it for 'what is known about NGC 6397', then ads_get_paper on the best hits. Summaries of abstracts are not a review of the papers.

The papers that one paper CITES (its reference list), from ADS, most cited first by default.

Search NASA ADS for papers. Give any of: query (ADS syntax, e.g. 'abs:"Gaia" AND bibstem:A&A'), author ('Lastname, F'), first_author, title words, abstract words, object (a name ADS resolves via SIMBAD/NED), bibcode, year_from/year_to, refereed_only. Returns title, authors, year, venue, citation count, DOI/arXiv links and provenance (the exact ADS query). Needs an ADS API token in ADS_API_TOKEN ('ads_not_configured' if absent).

Metadata and abstract of ONE arXiv paper by identifier (new '2101.01234', versioned '2101.01234v2' or old 'astro-ph/0601001'), with journal reference if the authors gave one.

Recent arXiv submissions of a category (the listing of the last days), newest first, with the start of each abstract. Example uses: 'what is new in astro-ph.GA'.

Search arXiv (all of it, or one category). Give any of: query (words), title, author ('Lastname' or 'Lastname, F'), abstract words, category (e.g. astro-ph.GA). Needs no token. arXiv asks for one request every three seconds: calls queue and repeats are cached. Preprints are not peer reviewed.

The archives archive_search knows (SDSS, Pan-STARRS, Legacy Surveys, DESI, MAST, ESO, IRSA, HEASARC, CADC, ALMA, Gaia): what each holds, its products, whether it can be queried from here, and its web links.

Search ONE archive around a position (or named object) and return metadata, links and a small table: never the data themselves. archive: see archive_list (sdss, panstarrs, legacy_survey, desi, mast, eso, irsa, heasarc, cadc, alma, gaia_dr3). `product` picks the table where an archive has several; `table` picks another IRSA/HEASARC table. Example: archive_search(archive='mast', target='M 51', radius_arcmin=3).

Probe every upstream service this server uses with a tiny request and report reachable or not, HTTP status and time. Useful when an archive answers with an error.

CDS cross-match of a SMALL list of positions (at most 100) against a catalogue: for each position the nearest source within the radius. catalogue: gaia_dr3, 2mass, allwise, panstarrs, sdss, simbad, or 'vizier:<table id>'. Example: cds_crossmatch(positions=[[279.2347, 38.7837]], catalogue='gaia_dr3', radius_arcsec=5).

Run ONE read-only ADQL SELECT on the Gaia archive (gaiadr3.gaia_source, gaiadr3.astrophysical_parameters, ...). Anything but a single SELECT is refused; no comments, no semicolon; TOP is added or lowered to the row cap. Example: SELECT source_id, parallax FROM gaiadr3.gaia_source WHERE parallax > 100.

Gaia DR3 cone search (ESA archive): source_id, position, parallax, proper motion, G/BP/RP, radial velocity, RUWE, nearest first. Radius in arcsec, at most 3600. Example: gaia_cone(ra=279.2347, dec=38.7837, radius_arcsec=60, max_g_mag=15).

Everything useful about ONE Gaia DR3 source by source_id: astrometry, photometry, quality flags and the GSP-Phot astrophysical parameters when present. Example: gaia_source(source_id='2099719994020044800').

List HiPS sky surveys (all-sky image sets) from the CDS HiPS list by keyword, for example 'DSS', 'PanSTARRS', 'WISE', 'Legacy'. Returns the survey id to use in image_cutout.

An image cut-out of the sky from a HiPS survey (CDS hips2fits): returns the LINK to the picture, its size in bytes and the pixel size; the picture itself is not returned. Example: image_cutout(target='M 51', fov_arcmin=10, hips='CDS/P/DSS2/color'). Format jpg, png or fits (fits: at most 512 pixels).

NED (NASA/IPAC Extragalactic Database) lookup of ONE object by name: preferred name, position, object type and redshift with its reference. Example: ned_object(name='M101').

Name to position: resolve an object name with CDS Sesame (SIMBAD, NED, VizieR resolvers) into ICRS coordinates, object type and aliases. Example: resolve_name(name='M 51') to ra 202.4696, dec 47.1952. Use it before a cone search when the person gives a name.

SIMBAD cone search: objects within a radius of a position (or of a named object), nearest first: identifier, type, coordinates, V magnitude, redshift. Radius in arcmin, at most 120. Example: simbad_cone(target='M 51', radius_arcmin=2, object_type='Galaxy').

SIMBAD (CDS) record of ONE object by name: main identifier, coordinates, object type, spectral type, parallax, proper motion, radial velocity and redshift, magnitudes per filter and the list of identifiers. Example: simbad_object(name='Vega').

Column metadata of one VizieR catalogue: name, unit, UCD, type and description. Example: vizier_columns(catalogue='I/355/gaiadr3').

Cone search in ONE VizieR catalogue around a position (or named object). Returns the chosen columns (default: the catalogue's standard ones). Example: vizier_cone(catalogue='II/246/out', target='Vega', radius_arcsec=30). Radius in arcsec, at most 3600.

Find VizieR catalogues (tables) by keywords in their name or description, for example 'Gaia', '2MASS', 'cepheid period'. Returns the catalogue identifier (such as I/355/gaiadr3) and its title. Use the identifier in vizier_columns and vizier_cone.

Search the Virtual Observatory registry for TAP (table access) services by keywords in their title or description, for example 'radio continuum' or 'supernova'. Returns title, identifier and the TAP address. If the registry cannot be reached, this server's own list of known services is searched instead (the answer says which). A service found here can be used in vo_tap_tables and vo_tap_query.

Run ONE read-only ADQL SELECT on a TAP service (same names as vo_tap_tables). Refused unless it is a single SELECT; TOP is added or lowered to the row cap; the call has a time limit. Look at the tables first with vo_tap_tables. Example: vo_tap_query(service='irsa', query="SELECT designation, ra, dec, w1mpro FROM allwise_p3as_psd WHERE 1=CONTAINS(POINT('ICRS',ra,dec),CIRCLE('ICRS',202.48,47.23,0.01))").

List the tables of a TAP service, or the columns of one table (give `table`). `service` is a built-in name (simbad, vizier, gaia, ned, datalab, mast, eso, irsa, heasarc, cadc, esasky, euclid, alma, gavo) or the https TAP address returned by vo_registry_search. Example: vo_tap_tables(service='irsa', table='allwise_p3as_psd').