<p>This problem was studied in <a href="http://iopscience.iop.org/article/10.1088/0256-307X/13/6/021/meta;jsessionid=EEAA7E4E254BA2B9226DD9D56C5C8404.c4.iopscience.cld.iop.org" rel="nofollow">Yu &amp; Zheng (1995)</a>, who evaluated the effects of the change in the Sun's mass over time and the change in a comet's mass over time, for the case of <a href="https://en.wikipedia.org/wiki/Comet_Shoemaker%E2%80%93Levy_9" rel="nofollow">Shoemaker-Levy 9</a>, which had recently crashed into Jupiter. Given their mass model for the comet (Equation 6), they found that the Sun's mass loss created an increase in semi-major axis of about 8.5 centimeters per year, whereas the comet's mass loss created an increase in semi-major axis of about 10,000 kilometers per year.</p>

<p>Several things to note:</p>

<ul>
<li>The comet orbited Jupiter prior to breaking up, so it did not come as close to the Sun as most short-period comets.</li>
<li>Mass loss rates can change over time, depending on the distance from the Sun.</li>
<li>Shoemaker-Levy 9 should not be considered a normal comet, in any sense, given its orbit and eventual destruction.</li>
</ul>

<p>10,000 kilometers a year, though, is nothing to sniff at. Over the course of an orbit, that can be quite a lot - although keep in mind that longer orbits involve much larger semi-major axes - and I'd argue that it should be observable, given the correct calculations of how the orbit should evolve over time.</p>

CC BY-SA 3.0
2016-10-01T07:44:23.513Z
Your answer is good in its own but not as specific as i asked.
What argument is right but you don't specifically mention that what kind of that change may be? 
My field is not astronomy so please bear with me.
Shuji
CC BY-SA 3.0
2016-10-01T15:56:31.563Z
Why does comet orbit change? Because the mass loss is asymmetric?
ProfRob
CC BY-SA 3.0
2016-10-01T22:32:41.773Z
@ShujaatAliKhan The orbital parameter we're concerned with is the [semi-major axis](https://en.wikipedia.org/wiki/Semi-major_and_semi-minor_axes), one half the distance between the two furthest points in the elliptical orbit of the comet. It increases as the comet looses mass.
HDE 226868
CC BY-SA 3.0
2016-10-01T22:37:21.817Z
@RobJeffries It turns out that the mass loss of the comet causes a tangential acceleration perturbation, coming from matter being blown off the comet at a constant velocity.
HDE 226868
CC BY-SA 3.0
2017-09-19T18:30:27.083Z
So with every revolution a comet actually becomes more eccentric?  That is interesting.  If you wanted to cause the opposite and reduce the semi-major axis, I suppose you could 'block' the mass losses natural direction and only allow the opposite direction to be exposed to mass loss.
Brooks Nelson
CC BY-SA 3.0
2016-09-30T23:40:24.597Z
2016-09-30T23:40:24.597Z
HDE 226868
<p>Comets lose their mass through water evaporation due to close encounter with sun, so my question is does the loss of mass create an observable change in a comet's orbit? What kind of change that may be shrinking orbit or expanding orbit?</p>

<orbit><the-sun><comets>
Does the loss of mass create an observable change in a comet's orbit?
Shuji
# Does the loss of mass create an observable change in a comet's orbit?

(Asked by: username_0 on 2016-09-30)

Comets lose their mass through water evaporation due to close encounter with sun, so my question is does the loss of mass create an observable change in a comet's orbit? What kind of change that may be shrinking orbit or expanding orbit?

**Tags:** orbit, the-sun, comets

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## 1 answers

### Answer by username_1 on 2016-09-30. Score: 3 | Accepted answer

This problem was studied in [Yu & Zheng (1995)](http://iopscience.iop.org/article/10.1088/0256-307X/13/6/021/meta;jsessionid=EEAA7E4E254BA2B9226DD9D56C5C8404.c4.iopscience.cld.iop.org), who evaluated the effects of the change in the Sun's mass over time and the change in a comet's mass over time, for the case of [Shoemaker-Levy 9](https://en.wikipedia.org/wiki/Comet_Shoemaker%E2%80%93Levy_9), which had recently crashed into Jupiter. Given their mass model for the comet (Equation 6), they found that the Sun's mass loss created an increase in semi-major axis of about 8.5 centimeters per year, whereas the comet's mass loss created an increase in semi-major axis of about 10,000 kilometers per year.

Several things to note:

* The comet orbited Jupiter prior to breaking up, so it did not come as close to the Sun as most short-period comets.
* Mass loss rates can change over time, depending on the distance from the Sun.
* Shoemaker-Levy 9 should not be considered a normal comet, in any sense, given its orbit and eventual destruction.

10,000 kilometers a year, though, is nothing to sniff at. Over the course of an orbit, that can be quite a lot - although keep in mind that longer orbits involve much larger semi-major axes - and I'd argue that it should be observable, given the correct calculations of how the orbit should evolve over time.

> **Comments:**
> **username_0**: Your answer is good in its own but not as specific as i asked. What argument is right but you don't specifically mention that what kind of that change may be?  My field is not astronomy so please bear with me.  
> **username_2**: Why does comet orbit change? Because the mass loss is asymmetric?  
> **username_1**: @ShujaatAliKhan The orbital parameter we're concerned with is the [semi-major axis](https://en.wikipedia.org/wiki/Semi-major_and_semi-minor_axes), one half the distance between the two furthest points in the elliptical orbit of the comet. It increases as the comet looses mass.  
> **username_1**: @RobJeffries It turns out that the mass loss of the comet causes a tangential acceleration perturbation, coming from matter being blown off the comet at a constant velocity.  
> **username_3**: So with every revolution a comet actually becomes more eccentric?  That is interesting.  If you wanted to cause the opposite and reduce the semi-major axis, I suppose you could 'block' the mass losses natural direction and only allow the opposite direction to be exposed to mass loss.  

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