How To Write An Essay In 25 Minutes On Elliptical

NASA's Chandra X-ray Observatory has shed new light on the mystery of why giant elliptical galaxies have few, if any, young stars. This new evidence highlights the important role that supermassive black holes play in the evolution of their host galaxies.

Because star-forming activity in many giant elliptical galaxies has shut down to very low levels, these galaxies mostly house long-lived stars with low masses and red optical colors. Astronomers have therefore called these galaxies "red and dead".

Previously it was thought that these red and dead galaxies do not contain large amounts of cold gas - the fuel for star formation - helping to explain the lack of young stars. However, astronomers have used ESA's Herschel Space Observatory to find surprisingly large amounts of cold gas in some giant elliptical galaxies. In a sample of eight galaxies, six contain large reservoirs of cold gas. This is the first time that astronomers have seen large quantities of cold gas in giant elliptical galaxies that are not located at the center of a massive galaxy cluster.

With lots of cold gas, astronomers would expect many stars to be forming in these galaxies, contrary to what is observed. To try to understand this inconsistency, astronomers studied the galaxies at other wavelengths, including X-rays and radio waves. The Chandra observations map the temperature and density of hot gas in these galaxies. For the six galaxies containing abundant cold gas, including NGC 4636 and NGC 5044 shown here, the X-ray data provide evidence that the hot gas is cooling, providing a source for the cold gas observed with Herschel. However, the cooling process stops before the cold gas condenses to form stars. What prevents the stars from forming?

A strong clue comes from the Chandra images. The hot gas in the center of the six galaxies containing cold gas appears to be much more disturbed than in the cold gas-free systems. This is a sign that material has been ejected from regions close to the central black hole. These outbursts are possibly driven, in part, by clumpy, cold gas that has been pulled onto the black hole. The outbursts dump most of their energy into the center of the galaxy, where the cold gas is located, preventing the cold gas from cooling sufficiently to form stars.

The other galaxies in the sample, NGC 1399 and NGC 4472, are also forming few if any stars, but they have a very different appearance. No cold gas was detected in these galaxies, and the hot gas in their central regions is much smoother. Additionally, they have powerful jets of highly energetic particles, as shown in radio images from the National Science Foundation's Karl G. Jansky Very Large Array. These jets are likely driven by hot gas falling towards the central supermassive black holes. By pushing against the hot gas, the jets create enormous cavities that are observed in the Chandra images, and they may heat the hot, X-ray emitting gas, preventing it from cooling and forming cold gas and stars. The centers of NGC 1399 and NGC 4472 look smoother in X-rays than the other galaxies, likely because their more powerful jets produce cavities further away from the center, where the X-ray emission is fainter, leaving their bright cores undisturbed.

A paper describing these results was published in the February 25, 2014 issue of the Monthly Notices of the Royal Astronomical Society and is available online. The first author is Norbert Werner from Stanford University in California.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Mass., controls Chandra's science and flight operations.

Fast Facts for NGC 1399:
Credit X-ray: NASA/CXC/Stanford Univ/N.Werner et al.
Release Date May 30, 2014
Scale Image is 6.5 arcmin across. (about 130,000 light years)
Category Normal Galaxies & Starburst Galaxies
Coordinates (J2000) RA 03h 38m 29.08s | Dec -35� 27' 02.67"
Constellation Fornax
Observation Dates  3 pointings between 18 Jan 2000 and 08 Jun 2008
Observation Time 40 hours 32 min (1 day 16 hours 32 min)
Obs. IDs  319, 4172, 9530
Instrument ACIS
References Werner, N. et al, 2014, MNRAS 439, 2291-2306; arXiv:1310.5450
Color Code X-ray (Blue)
Distance Estimate About 65 million light years
Fast Facts for NGC 4472:
Credit X-ray: NASA/CXC/Stanford Univ/N.Werner et al.
Release Date May 30, 2014
Scale Image is 6.5 arcmin across. (about 100,000 light years)
Category Normal Galaxies & Starburst Galaxies
Coordinates (J2000) RA 12h 29m 46.90s | Dec +08� 00' 13.00
Constellation Virgo
Observation Dates  12 Jun 2000
Observation Time 11 hours 6 min
Obs. IDs  321
Instrument ACIS
References Werner, N. et al, 2014, MNRAS 439, 2291-2306; arXiv:1310.5450
Color Code X-ray (Blue)
Distance Estimate About 55 million light years
Fast Facts for NGC 4636:
Credit X-ray: NASA/CXC/Stanford Univ/N.Werner et al.
Release Date May 30, 2014
Scale Image is 6.5 arcmin across. (about 95,000 light years)
Category Normal Galaxies & Starburst Galaxies
Coordinates (J2000) RA 12h 42m 49.87s | Dec +02� 41' 16.01"
Constellation Virgo
Observation Dates  3 pointings between 26 Jan 2000 and 15 Mar 2003
Observation Time 55 hours 57 min (2 days 7 hours 57 min)
Obs. IDs  323, 3926, 4415
Instrument ACIS
References Werner, N. et al, 2014, MNRAS 439, 2291-2306; arXiv:1310.5450
Color Code X-ray (Blue)
Distance Estimate About 50 million light years
Fast Facts for NGC 5044:
Credit X-ray: NASA/CXC/Stanford Univ/N.Werner et al.
Release Date May 30, 2014
Scale Image is 6.5 arcmin across. (about 190,000 light years)
Category Normal Galaxies & Starburst Galaxies
Coordinates (J2000) RA 13h 15m 23.97s | Dec -16� 23' 08.00"
Constellation Virgo
Observation Dates  2 pointings on 19 Mar 2000 and 07 Mar 2008
Observation Time 28 hours 39 min (1 day 4 hours 39 min)
Obs. IDs  798, 9399
Instrument ACIS
References Werner, N. et al, 2014, MNRAS 439, 2291-2306; arXiv:1310.5450
Color Code X-ray (Blue)
Distance Estimate About 102 million light years

If you have 30 minutes to spare and some calories to burn, try this elliptical workout. It's fun and fast moving, with speedy intervals to chew up calories and some backward action to work your backside. The cooldown even includes some hands-free time to challenge your core and help slow you down at the end.

To check out the workout, keep reading.





TimeResistanceSPM*Notes
00:00-3:00
4
130-140Warm up
03:00-5:00
5
150Warm up
05:00-6:00
5
170RPE** 8
6:00-8:00
5
140RPE 5
8:00-9:00
5
180RPE 8
9:00-10:00
5
140RPE 5
10:00-12:00
7
180RPE 8
12:00-13:00
7
130Backward
13:00-14:00
9
160-170RPE 8
14:00-15:00
5
130RPE 5
15:00-16:00
9
170-180RPE 8
16:00-17:00
7
130RPE 5
17:00-18:00
9
180RPE 8-9
18:00-20:00
7
130Backward
20:00-22:00
7
180-190RPE
22:00-23:00
5
130RPE 5
23:00-25:00
7
170-180RPE 8
25:00-28:00
5
140Cooldown
28:00-30:00
4
130No Hands

*SPM = Strides Per Minute
**RPE = Rate of Perceived Exertion
Incline = 20 percent

This workout burns about 240 calories (for a 130-pound woman). My elliptical has a fixed incline of 20 percent, so set your machine with at least some incline if you can. As always, if this is too easy or too hard, change the amount of resistance and the strides per minute.

If this workout doesn't float your boat, check out my other cardio plans. I have received comments from some readers that their elliptical machines don't have SPM readout. For a machine that uses RPM (revolutions per minute), simply halve the number listed for SPM. If your machine uses MPH (miles per hour), use the rate of perceived exertion chart.

Click here for an image-free printable version of this workout.

Image Source: Thinkstock

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