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Archiving the Past for the Future

There is a group here at Goddard is called the HEASARC – High Energy Astrophysics Science Archive Research Center. This is where we keep data from old and new satellites. Even though every new satellite is an improvement over the last in one way or another, it is important to keep old data, with the expertise to go with it.

Think of Halley’s Comet – when Edmund Halley calculated the orbit of this comet from observations in 1682, he was able show that it was the same as the comets of 1531 and 1607 because there were sufficiently detailed records from those appearances.

Halley's Comet
Halley’s Comet. Credit: NASA

We now know of even earlier appearances of Halley’s Comet, dating back at least to the Chinese record of of a comet in 240 BC. Chinese court astrologers had a habit of making careful records of not only comets but novae and supernovae, which they collectively called “guest stars.” These records are invaluable to today’s astrophysicists who also use modern telescopes and satellites. For example, historical records can give you the precise age of a supernova since the explosion.

John Russell Hind
John Russell Hind
Here is another example – this time involving an actual archive. On April 28, 1848, the British astronomer John Russell Hind found a new 5th magnitude star in Ophiuchus where none was seen before. He didn’t know it at the time but what he discovered was a nova – a nuclear explosion on the surface of a white dwarf star. Unlike supernovae (much more powerful explosions that destroy the star), novae DO repeat – we think a typical recurrence time may be 10,000 to 100,000 years, although rare examples are known to repeat every few decades. But Hind and his contemporaries did not know that.

Hubble's View of Nova T Pyxidis
Hubble’s View of Nova T Pyxidis. Credit: NASA

Strangely enough, there is an entry in Flamsteed’s catalog published in the early 18th century for “52 Serpentis,” located near the position of this new star that nobody else had ever seen. In 1848, the consensus was that 52 Serpentis was a spurious star, arising from a mistake on Flamsteed’s part. Or was it? With the discovery of the nova, should they reconsider this?

Hind was allowed to view the original documents preserved at the Royal Observatory, Greenwich. These originals show that, on June 16, 1690, Flamsteed measured the position of “52 Serpentis” relative to that of eta Ophiuchi, but had a typo in the position of eta Ophiuchi, hence creating a spurious entry in his catalog. Hind’s “letter respecting his changing star” is worth reading in its entirety if you are a fan of old mysteries.

X-ray and gamma-ray sky are far more violent than that in visible light – strongly variable objects are the norm, not the exception. Many astronomers consult the HEASARC routinely to supplement the latest & the greatest data that they have just gotten. Some projects that involve, say, a 30-year history of an X-ray binary, are possible only with an archive like HEASARC. It is not just a collection of data, but also a collection of expertise, with friendly staff ready to help any astronomer navigate through the peculiarities of old missions.

Back to Hind: one of the things Hind said in his letter resonates with me:

“It is a practical proof of the almost imperative necessity of preserving original observations, notwithstanding the observer himself may fancy he has guarded against all possible sources of error in his published results.”

That is, always be prepared to the original source. This is something to consider in the age of large scientific projects in astronomy and elsewhere, where the temptation may exist to just look at highly processed data without touching the raw data. I, for one, think that would be a huge mistake.


1 Comment

  • gerry says:

    And don’t forget the crew At McMoons out in Ca using old refurbished AMPEX tape equipment re-making the LOIRP pics for NASA on a SHOESTRING BUDGET!!!! Whose going to be saving the old floppy drives, DVD players and HDD’s of today for future DATA Mining from laptops and desktops?

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