Another One Bites The Dust – ROSAT Satellite Coming Down Soon

Jupiter and the waning gibbous moon shine between fall trees late last night. Photo: Bob King

Darkness comes early in mid-October. For some, the disappearance of daylight is tough to handle. We feel like moles in a dark tunnel from dinnertime until the next morning’s breakfast. Most people seem to be more in tune with daylight instead of darkness, yet many sky watchers have learned to embrace the night. The stars may be dim but getting to know them and the ragtag galaxies, planets and nebulae is like being in a room with a thousand candles. Their light and energy stimulate a reflective and peaceful state of mind as satisfying in its way as streaming rays of sunshine. As daylight trickles away, I hope you’ll also find light and inspiration in the nights ahead.

Artist view of the German X-ray observatory ROSAT in space. Credit: German Aerospace Center

Looks like we’re in for Satellite Crash Act II. The German science observatory ROSAT, short for Roentgen Satellite, make its fiery plunge to Earth sometime between October 22-24 over a broad zone between latitudes 53 degrees north and south. Like the widely-publicized burn-up of NASA’s Upper Atmosphere Research Satellite (UARS), this satellite will also come down uncontrolled. Satellite trackers will only have a general idea of where it might land hours before it does. As with UARS, you shouldn’t be too worried. Since the Earth is 2/3 covered in water and thankfully still  blessed with a lot of uninhabited land, there’s a good chance it will crash without incident just as UARS did over the South Pacific.

When ROSAT finally does come down, it will be traveling at nearly 17,000 mph. The tremendous heat generated by friction with the air will burn up much of it up, but German scientists estimate 30 pieces will survive. Unlike UARS, ROSAT’s made of specially hardened components, so more of it will remain intact during re-entry – 3,750 lbs. of pieces will shower the ground versus an estimated 1,200 lbs for UARS. There’s  a 1 in 2,000 chance a person will be struck by the debris, which breaks down to a 1 in 14 trillion chance any particular individual will be hit.

An X-ray emitting neutron star (upper left) blinks out as the moon passes in front of it in these photos made by ROSAT. High-energy X-rays are shown in yellow, low energy ones in red. The moon scatters X-rays given off by the sun. Credit: ROSAT, MPE, NASA

ROSAT, an orbiting space telescope optimized to study the sky in X-ray light, is named after William Roentgen, the German scientist who discovered X-rays back in 1895. It operated for over 8 years beginning in 1990 before being shut down in 1999. Many high-energy objects in the universe emit X-rays including neutron stars, black holes, galaxy clusters and debris blasted into space by supernovas called supernova remnants. Since Earth’s atmosphere absorbs X-rays, telescopes made to focus this powerfully energetic light need to be lofted into orbit.

ROSAT created a detailed (for its time) map of the X-ray sky, took the first photos of X-rays bouncing off the moon and discovered X-ray emission in comets. It’s since been superseded by the Chandra X-ray Observatory with its much finer resolution.

This composite view of the entire sky in X-rays was made by ROSAT. The red is radiation emitted by hot gas in the halo of the Milky Way, the yellow from nearby gas bubbles at several millions of degrees and the highest energy blue from supernova remnants. Credit: ROSAT

You can still watch ROSAT track across your sky in the coming week before its plummet. Below are times when it’s visible from the Duluth, Minn. region. For times for your neighborhood, log on to Heavens Above and select your city and then click the ROSAT link. You’ll be shown a list of passes. When you click the date link, a nifty map pops up to help you know exactly where to look. You can also enter your zip code at the Spaceweather Flyby link and get times and general directions.

Like the space station, ROSAT travels from west to east across the sky, but it’s not nearly as bright. Expect to see a steady moving “star” of about 2nd magnitude or similar in brightness to those in the Big Dipper. It zips along fairly quickly now that its orbital altitude has been dropping from friction with the upper atmosphere.

* Tonight Oct. 14 beginning at 7:55 p.m. A brief and faint (magnitude 4) appearance low in the northwestern sky in the Big Dipper.
* Saturday Oct. 15 at 7:41 p.m. A better and brighter show tonight at mag. 2 1/2. Appears in the northwest and moves through the Big Dipper before fading away under the North Star.
* Sunday Oct. 16 at 7:25 p.m. Excellent high pass in the north at mag. 2.2
* Monday Oct. 17 at 7:08 p.m. Similar pass to yesterday. Bright at mag. 2.0

9 Responses

  1. Jay

    So what’s all this talk I’ve been hearing about Astriod 2005 YU 55? Is this something people need to worry about or should I just pay it no mind like comet Elenin?

    1. astrobob

      Not to worry, Jay. The asteroid will miss Earth by 192,000 miles. We’ve had much closer passes with no effects in the past few years.

  2. Debra

    Is it true that the sattelites they put up now must be made so that they all disintigrate when they come back down again

  3. les

    So comet eilenen is supposed to come by earth this weekend is it sat or sun?? And how far will it be again??? and when is that.other.asteroid the above guy mentioned coming by??? have comets been closer then elinen?

    1. astrobob

      There’s not much of Comet Elenin left. It’s closest approach to Earth is 22 million miles ( a very healthy distance) on Oct. 16-17. The asteroid is 2005YU55 and it passes 192,000 miles from Earth on Nov. 8. Yes, there have been a number of comets closer than Elenin over the years. None has effected our planet. Comet IRAS-Araki-Alcock passed only 3.1 million miles from us in 1983.

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